The Big Bang Theory prequel show continues to tackle its titular character's life as he lived with his family in Texas. This was before he moved to Pasadena and eventually met his life-long friends and future wife. But despite being a period piece, the show's narration, which is delivered by adult Sheldon is giving hints as to what his life is now after the original sitcom wrapped.
The shows are supposed to exist in the same reality, with Young Sheldon being CBS' way of taking advantage of The Big Bang Theory's massive fan community despite it already having ended after 12 seasons. However, the spin-off isn't known for preserving continuity, deliberately breaking it for the sake of the prequel's own storytelling. More recently, however, Young Sheldon is trying to make amends for it by being more mindful of their narratives and how they affect what was established in its parent series.
Interestingly, however, Young Sheldon season 4, episode 15 titled "A Virus, Heartbreak, And A World of Possibilities," contradicted itself, effectively creating a plot hole about what it revealed about Sheldon and Amy's married life after The Big Bang Theory ended. In the episode, the narration hinted that adult Sheldon is recalling the events of the outing around the present time at the age of coronavirus where social distancing is still cool — that's around two years since the original show ended in 2019. This fits well with the narrative the sitcom was telling; the problem is, it doesn't line up with the established timeline in the Young Sheldon season 4 premiere where adult Sheldon revealed that he and Amy have a son who has already had a graduation party. Granted that it's possible that the pair has a very intelligent kid, Leonard Cooper should still be around one or two years old, assuming that Amy was already pregnant when they won the Nobel Prize in Physics, and it's just not possible for him to have already been in school.
Since Young Sheldon has been purposefully vague about how far into the future the narration is from, there's also the fair argument that Sheldon may be telling the story of his childhood in a non-linear fashion. However, it's worth noting that it's also adult Sheldon who opens every episode of the spin-off with a "previously on" tag. This means that his of his childhood is done in a proper progression of events. The general idea of Amy's voice cameo in the Young Sheldon season 4 premiere was great; it allows CBS to build on the story of The Big Bang Theory even after it wrapped up. It will be a treat hearing the voices of the couple's friends like Penny and Leonard, especially since they were expecting when the original sitcom ended. But the spin-off needs to be more careful with smaller details like the aforementioned ones.
It's curious if Amy will make another cameo in the near future on Young Sheldon. After all, Jim Parsons and Mayim Bialik have continued their working relationship past The Big Bang Theory in the new show, Call Me Kat. With the CBS period show running at least until 2024 after it was renewed for three more seasons, there's plenty of opportunities to bring her back moving forward.