It's not about how flexible you are at what age, whether you have three or thirty jackets, but in my opinion, it's about the fact that, no matter how old you are, you shell out a substantial sum for a house. And at least I am made in such a way - and I already was in my early twenties - that I want everything to be as perfect and good as possible. A house is not like a T-shirt from H&M that I wear twice and then I just don't like it anymore and it ends up in the clothes collection.
If I had had the opportunity, I probably would have built a house in my early twenties too - I was already designing houses just for fun back then. If I saw a great plot, I thought about what dream house I would have built on it, etc.
But, looking back: it would have been a completely different house than the one I built now, 30 years later. Whether I would have sold the first one by now - no idea. Probably not. Maybe remodeled, optimized, but I probably would still have it.
Only the discussion about whether at the beginning of your twenties you would more easily accept some planning mistakes, I find stupid, honestly. Even in your early twenties, you want/can try to get the optimum out of it.