I don't think we can judge Smith as being limited or lacking in coverage ability. He plays LB for his HS team because he can most affect the game at that level from the LB spot. Dude is a heat seeking missile. He had 37 tfls last season! That's more than most elite DE prospects get!
But, he did play deep safety as a sophomore and looked good doing it. He also has done the whole camp circuit all the way through the Opening finals and the 7-on-7 circuit (on the best team) playing DB and I haven't seen any reports indicating that Smith was out of place in coverage or deep in space. So, I think he has some more coverage ability to offer than what his HS LB role showcases.