To begin with, I completely get this theory, as laid out in the OP: that the Futurians got it wrong, this was a predestion/stable time loop scenario in which Heisei Godzilla was always formed this way, and they just didn’t realize there were two Godzillas. And I think it is the best way to rationalize the plot if you’re looking to understand it in traditional time travel terms.
Rewatching this last night, I don’t think that’s accurate. I would posit that the intent of the film is to posit a world where time travel changes occur at the moment time travel does, bringing a new world into being from that point forward- and as such, not actually altering the past, only altering the present moment into a world as it would have been from an altered past. Which, as time travel logic goes, makes far less sense- but also matches the narrative far better.
Consider the following:
-The Futurians’ computer calculated the theory from the book at a 98% probability of being accurate; this computer is later shown to be reliable.
-At the exact moment of the time travel (in 1991), Godzilla vanishes and King Ghidorah appears. I know the current theory just indicates they have trouble tracking him… but Godzilla disappearing and KG appearing at that exact moment? That seems a little less easy to spin as a simple tracking error.
-The characters (including time-travel-knowledgeable Futurians) seem content that they have erased Godzilla from history even though everyone still remembers him and knows who he is, indicating that alteration of the past is supposed to work that way, if successful.
-Godzilla is now in the spot that they sent him to in the past, and appears to get there instantly from the place that he was, where he disappeared from at the moment of time travel. It would have to be an enormous coincidence for Godzilla, who had been motionless for two years, to suddenly start moving so rapidly he that ongoing tracking suddenly lost him (he didn’t seem like he had that kinda speed in him, from the ANEB), to head exactly for the spot he’d been born 50 years earlier, just as King Ghidorah, who’d been around (hiding?) for 50 years, suddenly got picked up, and all precisely at the moment that time travel occurred.
-When noting Godzilla’s size, the characters note that he was created with modern nuclear powers ‘this time’, as well as absorbing radiation from the sub. As opposed to Godzilla simply having been the same from Biollante and getting cured/enlarged by the sub. The characters are aware that the sub would have an effect- but then, Godzilla gets nuclear power in Return of Godzilla and doesn’t grow merely from that. The movie seems very intent on positioning this as due to the different nature of his origin. The Futurians also refer to it as his ‘second birth.’ Yes, these characters could be operating on an outmoded understanding based on a wrong theory (according to the accepted time travel model from this film)… but the idea that he now originated from the sub accident in the Berring Sea as opposed to the Bikini Atoll blast seems to be very much what the film is suggesting.
-Last but not least, I floated the idea that there are three 23rd century futures- the Futurians’, with a superpowered Japan that was untroubled by Godzilla, a second , where Japan had been destroyed by Godzilla, and the third and final, which would be super-advanced from the reverse-engineering of future-tech left behind in the 90s at the end of the movie. This time around, I realized that dialogue confirms this; in the sub scenes, the future fellow refers to Japan as a ‘needy country’ that had been destroyed by Godzilla and nuclear waste- indicating that the timeline had indeed changed from the Futurians’ origin based on the actions in the film.
All of this taken together suggests to me that- while the logic of it may not fit a typical understanding of time travel- this film is indeed positing that Godzilla’s past had been altered by the events in this film, successfully; that, based on the nature of their odd time travel model, RoG and vs. Biollante still happened… but that at the moment the time travel craft departed and returned to 1991, Godzilla did indeed vanish- replaced by this new version of Godzilla with an alternate past whose visit to Japan here was, for him, his first.
History changed- but only from this moment in 1991-onward, with every preceding moment untouched (however nonsensical that is when you think about it), but the kaiju themselves altering states instantly to the nature they would have been from the revised history (KG coming into existence on Lagos, ANEB-infected Godzilla from Bikini Atoll ceasing to exist, sub-mutated Godzilla popping into existence in the Berring Sea; both at, essentially, their first moment of existence, with no prior history).*
It’s the only thing that matches all the dialogue and concepts in the film- which the prevailing time travel theory, while more logical in its temporal mechanics, simply doesn’t. As fans, we’ve concocted another model that gives the writers far more credit than they deserve; but I’d suggest neither the idea that this was a stable time loop, nor a situation in which RoG and Biollante were erased from history; but a weird, third option in which the past still happened for everyone except Godzilla, who now has a different history.
*This confusing model- with past changes resulting in an instantaneous change to the present to the new status quo, despite not undoing anything prior to that moment- does also seem to be what’s used in Rebirth of Mothra III, meaning that at least there is a consistent, nonsensical cosmological model for time travel in this era?
It’s part of my secret plan to create a fifth column in the US, pre-emoting our glorious conquest and the creation of the Canadian Empire, upon which the sun will consistently set after less than eight hours of daylight.
The grace of God is a greater gift than we can truly fathom; undeserved mercy is a kindness humbling in its sheer scope.
The Zone Fighter campaign is complete, with all episodes subtitled! PM me if you need a link location.