I have never met him but a few people i'm close to grew up with him and lived with him at Michigan, they said that he's always been difficult and stand off-ish, maybe that part of him is getting worse with age. He's rubbed administrators the wrong way in the past and it could create problems in AA. I don't think this comes as a surprise to anyone though
To me, in his public personae, which is probably what he's like off camera, he comes off as "task oriented" or "task focused," which can probably make one seem a little aloof or stand offish.
Like the Cowherd interview was a "task," although it was just chatting about what Cowherd was asking him about, which isn't really doing a task, it's chatting, which Harbaugh kind isn't focused on; he likes stuff with a purpose.
So to try to pretend to out of the (Go) Blue "sell" Michigan to an imaginary recruit that Cowherd is pretending to be, it isn't a task, not really, and I can see Harbaugh not seeing the purpose in it.
All the coaches that Cowherd mentioned that he claimed "sell" their programs to Cowherd more effectively, I think that's Cowherd blowing his own horn; I doubt a single high school prospect listens to the Colin Cowherd show to figure out what coach he wants to play for; aren't they all walking around with head phones listening to beats, and stuff, instead?
Harbaugh apparently recruited really well at Stanford; I don't know if he was at San Diego long enough to have a record of recruiting success.
I expect he'll have success recruiting at Michigan; but not doing it on the Colin Cowherd show on the radio;but doing it the old fashioned way and stuff.
As far as rubbing people the wrong way, he probably can, but he has one boss, and one boss's boss at Michigan; those are pretty much the only people who matter except for the ACs and players, and at the college level anyway, they all seem to have loved him in the past.