LOL, my Shire gelding just started looking like an actual draft this year - and he'll be turning 5 this summer. He grew upward pretty quick, but didn't fill out in his chest and bum for the longest time. I didn't even get on him until late last summer (when he turned 4).
Horses that are wide and thick like drafts always seem SO much bigger to me than they actually are - I always think my gelding is at least 17.2hh but in reality he's probably no taller than 17hh, LOL. Not to say that they can't get that tall! I've seen/heard of some drafts that are crazy tall - not 20hh, but 18/19hh. Definitely not unheard of - it's more the lack of pictures and age that is getting to me.