Well, they did note Hasslein's theory in Planet of the Apes as well. While 2000 years had passed for the rest of the universe, only about a year and a half or so had passed for the astronauts, according to the clock on the ship.
That's not Hasslein's theory, it's Einstein's (time dilation). But it's still a completely different thing from a reversible time warp like the third film established.
The TV series is hard to look at in the same continuity of the movies....
It wasn't even trying to be. Like most TV adaptations of movies back then, it was its own separate reality that took elements from the movies and put them together in a new way. Similarly, the Logan's Run series was an overt "reboot" (as we'd call it today) from the movie, retelling the basic plot of the movie in an alternate way in the first 10-15 minutes of the pilot and then going in their own direction from there, as well as changing a ton of stuff about the movie's version of the domed city (like leaving out the sexual hedonism and giving its people more family-friendly 20th-century beliefs about love and relationships). And there were a bunch of other shows that were only loose adaptations/remakes of movies rather than in-continuity sequels, like Alice, M*A*S*H, The Dukes of Hazzard (from Moonrunners), House Calls, The Paper Chase, and so on. It used to be the norm for TV adaptations to be remakes rather than continuations. I find it strange that people today seem to expect the Planet of the Apes TV series to be in the movies' universe.