Warning! Spoilers ahead for Young Sheldon season 5.
Sheldon's (Iain Armitage) admission in Young Sheldon season 5, episode 8 undermines The Big Bang Theory's emotionally-satisfying finale. CBS is able to continue capitalizing on the popularity of geek-centric sitcom years after it wrapped up in 2019 through its prequel series. Young Sheldon tackles adult Sheldon's (Jim Parsons) life in Texas before moving to Pasadena and meeting his friends. But while the shows supposedly exist in the same reality, there are several inconsistencies between them, including its latest one that leads to weakening the otherwise well-done The Big Bang Theory finale.
Due to its popularity, CBS was still looking to order at least one more season of The Big Bang Theory before its last year aired. Everyone was willing to return as revealed by Kaley Cuoco and Johnny Galecki, who played on-screen couple, Penny and Leonard. However, Parsons had other things in mind. He thought that they've done everything that they can with their characters and it was time for him to move on from the sitcom. Instead of continuing with an incomplete cast, the people involved in The Big Bang Theory ultimately decided to end the show altogether. And despite a rather uneven last season, CBS was able to craft a great send-off for the Pasadena gang.
In The Big Bang Theory finale, the group flew to Stockholm, Sweden to accompany Sheldon and Amy (Mayim Bialik) as they receive their Nobel Prize in Physics for their work on Super Asymmetry. However, Sheldon's antics ruined the trip when he started acting self-centered, dismissing Howard (Simon Helberg) and Bernie's (Melissa Rauch) worries about leaving their two young kids at home, while being indifferent to the news that Leonard and Penny were expecting their first child. Amy had to reprimand her husband for his behavior, but before he could even apologize for it, his friends decided to still show up and watch him achieve his biggest dream. As explained in the show, the reason why the Pasadena gang tolerated Sheldon for such a long time was because his insensitivity and selfishness weren't intentional. But, that may not actually be the case. In Young Sheldon season 5, episode 8 titled "The Grand Chancellor and a Den of Sin," he acknowledged that he actually has the tendency to make everything about him, and he's quite good at it. This implies that his self-centered nature may be more calculating than the original Big Bang Theory characters supposed, casting Sheldon in a completely different light.
The spin-off prequel doesn't actually make a big fuss about this particular line. Sheldon is merely trying to convince Dr. Linkletter (Ed Begley Jr.) that decreasing science requirements at school isn't a good idea. In an effort to stop him from blabbing, the professor tells him that the change in East Texas Tech's policy doesn't affect him. But the kid genius retorts by saying that he's good at making things all about him. Based on Sheldon’s admission, it means that adult Sheldon was aware of his antics throughout The Big Bang Theory; that includes every single time he hassled his friends for his convenience. Most importantly, this also implies that the Pasadena gang deciding to forgive him before he could even apologize for his behavior in The Big Bang Theory finale was wrong. Sheldon didn't deserve it, especially from Penny and Leonard, who had been nothing but patient and understanding with him.
To be fair, Sheldon does struggle with his social skills as seen with his lack of true friends in Young Sheldon. Incidentally, this is where his twin sister, Missy (Raegan Revord) shines. Perhaps it would've been more helpful to him if his The Big Bang Theory friends didn't easily let his transgressions go. As George (Lance Barber) said, coddling wouldn't do him any good.