Estrogen does slow their aging. They often do look younger than other men their age if they’ve been on it for a while.
Of course, TIMs who pass well enough to look like a woman look old for their age when seen as female. 26 year old semi-convincing TIMs look 46.
This is definitely true. One of my better male friends used to be a TIM and started hrt when he was 15–because he was so young (far too young) he started genuinely looking like a female over time, but he literally looked like he was a 25 year old woman when he was 16. The exact opposite happens to TIFs.