Ignoring the fact that this rumor (and this thread) is over a year old at this point, and there have been no new indicators to suggest that the described feature will ever actually come to fruition...
While that would certainly be annoying, I'm afraid it wouldn't be particularly surprising. Various companies frequently do some form of feature exclusivity; they usually justify it by saying that the new software feature requires something specific that's only included in the newer hardware. Then the modding crowd comes along behind and demonstrates that -- with some slight tweaks-- the new software and/or features mostly work just fine on the older hardware. It's a well-trod path that we've seen many times before: it's happened with macOS, Windows, Android and likely other products.
So... is what you describe likely? Yeah, kind'a. (Again, assuming that the rumored feature is ever implemented in the first place.) But... crazy? Only in-so-much as we all know that the real reason for software exclusivity is -- as always -- an obvious profit motivation.