It's genetics and more estrogen receptors that cause a female shape. Unless you start before puberty, someone at 33 could have a better effect then someone at 20. Just being 20 doesn't mean you'll have great results. It's all genetics. I think the young age thing is pushed a tad too much and some may be disappointed as they've been led to believe well I'm 20 so...starting young is better don't get me wrong, but there are many other factors and I think genetics is more important then age unless your post 40. It's also height, should size, hand size, skull size, etc. These things are basically solidified by age 20. It's all about the estrige receptors and how many one has. The reason young is good is because a lot of men masculinize eve more as they age. Not all.
For instance, I'm 30 and I already have low T and high E for a male and I have a butt and 36 B boobs (before HRT) and I'm already seeing results, fairly good ones, mainly bigger nipples and I'm on a low dose of spiro but not of E. But I may be a rare case. If I started at 20, my results prob would have been a lot better I will admit. Most men don't have boobs and a butt and small size 8 womens shoes and tiny hands. I also look like a replica of my sister and mom while my brothers look like my father. Maybe I have some intersex thing but it doesn't matter, I'm MTF, with hopes of going stealth.