I honestly don't know why you are saying that. If Zoe and Mark are 27 and behaving that way, Alfie is at least 10 years older than them. Jokes aside, I don't see the silly Alfie you're talking about, I think he acts very much his age. His age is not like late 20s, he's a young adult, and he acts his age.
He doesn’t act that way all the time it’s the times when he’s overly hyper and does that same talk as he does every single time he’s acting that way that drives me nuts. Like he’s a salesman. The cheeky calm chill Alfie is so much better imo than the hyper overly unrealistic trying to sell me on something Alfie. And yes I see people say before Alfie is the immature one but he’s the most mature off camera I feel. Haha