Reading way too much into this.
A lot of people—even those with some level of status—keep their account private.
Lashlee doesn't need to do anything to "promote himself" outside of running a solid offense and scoring points.
As far as communicating with recruits, he can follow who he wants, DM them, text, engage, etc. Doesn't need a public setting to do that.
Diaz is Mr. Twitter—with his public account and big mouth; where did that get him this past season?
Winning is all that matters. Public account versus Private—won't mean a thing if Lashlee and this offense come to play this year.