It's not age it's puberty/growth spurt. If he's not turning heads after hitting growth spurt then take a look in the mirror. I agree kids don't just come out of no where - but lots of good players at 12-14 haven't really progressed yet b/c strength/size isn't there. Look at the Minnesota numbers , very few college commits even make varsity as a frosh - size/strength is just not there yet FOR MOST KIDS.
If size/strength is not there for "most kids", then those late developers should be comparable in size/strength to "most kids" and their athletic ability should enable them to still compete at a high level. That is, if they have the athletic ability to compete at the highest levels. The best players at U18 were not non-factors at U14, I don't care how big they were at the time. Size matters but athletic ability, skating, and hockey IQ matter more.