My DH has tried on other models of H loafer and finds them clunky (which is the style) and heavy (which is his objection and reason why he hasn’t bought any). He does own chypres, H boots, and other shoes, and wouldn’t wear them if he has to walk a lot. But everyone is different. So I would simply ask your son bc the Hermes last may not be the best fit for his foot, or it could be some entirely different reason (like he loves them and is saving them for a special occasion lol)
My DH has found that if they are too heavy or the balance feels wrong, break in may not change that. There are as many other options in as many price, style, weight, function, type category as there are shoes. DH personally finds Edward Green loafers (I believe the 202 last specifically) to be among the most comfy, but getting the exact right last (model), size, width, type matters. In comparison to Edward Green, he finds H shoes to run large). If a man is picky about fit, I find that they tend to go to a brand that specializes in that type of thing. JMO though, and good luck
Your son of course has a very considerate and generous parent to think of getting him such gorgeous shoes