On top of the evidence in the film, these new comments show a clear approval of the theory from Marvel.
After all, the producer describing Stan as being “above and apart” from the films feels intended to make it so fans can enjoy the theory without it breaking continuity. Still, it’s gratifying to get a semblance of confirmation all the same.
Of course, even with Feige’s statement the whole thing is rather tongue-in-cheek, intended more as a shout-out to fans than it is hinting at a more narratively-involved role for Lee.
The movie version of the all-seeing beings are very similar in design to their comic look, which does disprove Lee actually being one of them, making him instead an intergalactic traveling compatriot in the theory.