not on offense. Stanford band and Utah students were UC. A coach tackling or tripping a player, refs have some latitude there. But I'm really unsure that the Harlan impeding a BYU defender has an application.
Sideline interference generally only applies when contact is made with a referee so not sure it would apply here either
I'm totally guessing here, but like a ref being able to award a TD if a coach ran out and tackled or tripped a runner, I'd guess the same thing would apply in reverse here if Harlan being on the field was deemed as interference