It's not necessarily so that the reason that small guys are often slots is that they are quick and hard to cover.

It's that many of them have to play off the line of scrimmage because they're too easily rerouted and have a hard time getting separation. Fast doesn't equal separation, especially in the NFL where everyone is fast.

Having said that, the college game isn't the Pro game. Perhaps he CAN get off the line and CAN get separation, it's only that in college playing the slot fit the offensive system and enabled him to make big plays.

I don't know. Maybe Deadpool or someone who has evaluated him can opine as to whether he is capable of lining up on the line, out wide, and getting separation..... or not.