For me, they looked like them and now they don't. There's no alternate universe, no special plastic surgery, nothing special. They just happened to grow into another person and nobody questions it.
Heck, even with identical individuals in-universe, they're just people who look extremely similar. Fiction has this sort of hightened reality where Ben Affleck can play five characters in the same fictional universe, or Samuel L. Jackson can play four characters in the Tarantino-Verse, while also playing a character within a movie within the Tarantino-Verse.
If you a can accept that, then you can accept that some characters just happen to have a completely different face sometimes, and no one has any issues with it.
I will not pretend that Edward Norton looks like Mark Ruffalo during The Incredible Hulk, I'll just accept that within certain fiction you have to put aside "logic" when it's unimportant things like recasts and twins.
why do people think What If...? means something? Come on, it clearly only went as far BTS as Mark playing the Hulk in the MCU so they got him to voice Banner. If it was really that important, then what about the times where the film actor didn't reprise their role? Is Spider-Man retconed to sound like a different person before Infinity War? What If...? is set in alternate universes anyway.