I think the inside pressure is the arm length and wingspan issue. Campbell has limited reach so he sets up farther outside to avoid letting the player get around him and then tries to recover inside with his athleticism. If the player is too fast Campbell can't recover back inside like he can with less athletic college players.
Kennard is a R3 guy I think? If it is a faster guy Campbell will struggle like Thuney in the SB. Arm length is not just for punching. The wingspan issue is Campbell's shoulders are narrow limiting his reach and ability to push rushers wide and deep around the back of the QB, so he has to setup deeper exposing the inside.
Campbell is a good LT. With fast guys like Walker, Carter, etc., he will need a TE chip to limit their outside rush so Campbell can set up more inside. Clearly Campbell is 100x better than Lowe, but is not what I would look for in a #4 pick like Alt. Trent Brown was a R7 pick.
Did you see Mike Tice's analysis with his son? I am not a scout, just a guy on PatsFans.