Lot of people misconflating
height with
size in this thread. There is no
height cutoff to play in the NFL if you have the requisite size and skills, as much as some stupid GMs have historically used it to talk themselves out of star/generational prospects (Brees, Russ, Kyler, etc.). But there most certainly is a bare minimum
size threshold if you want to survive a now 17 game NFL season beating year in, year out.
And this kid absolutely does not meet it currently. Doesn't mean he isn't worthy of being drafted or that he won't or can't ever succeed in the league... it just means that he undeniably is going to have to lock himself in a gym and pack on 15+ lbs of lean, functional mass, bare minimum, if he ever wants to play a full season in the league without ending up in a wheelchair.
I know WR is a "skill" position and it's true you don't need to be some 6'4 230 jacked super soldier like DK Metcalf to be successful... but there's a reason why there's official weight classes in other sports like wrestling, boxing, etc. Don't matter how quick, agile, or "skilled" you are or how high your IQ is for the game... if your ~160 lbs soaking wet you are going to be
folded once beasts like Jamal Adams make contact with your brittle ass... and that's before you get into things like being asked to block or if god forbid a heavier defensive player that isn't just a safety/cb drills you on a blown up play. Like y'all were clowning that viral picture of pre-draft Kyler Murray imitating Bo Jackson for how small he looked... dude was literally
40 pounds heavier then than Smith is now. 
There is absolutely an unofficial "weight class" you have to make to survive in the NFL. Hopefully this young man goes to an organization with a good training staff that helps him reach it without losing too much of the quickness and mobility that made him a prospect in the first place.