In my experience (stepsons now 28 and 30), young men tend to be really particular about certain types of garments, and/or completely oblivious and just want to wear whatever is available. It’s so individual I wouldn’t attempt to anticipate someone else’s preferences!
My eldest stepson insisted he didn’t want anything extra to layer with when he lived in Boston for college...until he got into a Boston winter. He then welcomed the extra layering pieces we bought him. But he also worked as a bike courier and a mover, so lots of time outdoors. YMMV. He also turned his nose up at a lot of stuff until it was purchased on our dime. Admittedly, he was going through a hippie phase where he was convinced “the man” was trying to keep everyone down, but when “the man” (in the form of our credit card) got him into some nice-looking Lucky jeans and he could throw out the holey Goodwill pants he was wearing, he kinda forgot about how oppressed everyone was.
But I digress. The guys in my life seem to be down with long underwear if it’s cold enough to warrant an underlayer. It’s not for public viewing, after all! But if he’s really adamant, I say wait and see if he starts needing something more when the cold weather hits.