Well, unless cops start targeting permit holders to catch technical violations of the MPPA, they probably don't need to know a lot. Not many permit holders cause trouble.

If I was a cop, I'd focus more on drugs, DUI, and violent crimes, instead of the details of civilian permits.

The problem lies in ignorant cops assuming a guy with a gun has de facto committed a crime, and acting according to that misapprehension.

Yup; and we've seen just that, and, I think, some attempts by uncivil civil servants to use their lack of training as an excuse for, at a minimum, uncivil behavior.

Sure, that de facto assumption (would be/ is) the problem. But the fact that cops in general are not fascinated with enforcing the MPPA against permit holders would suggest that many cops are NOT necessarily "ignorant" about permit holders. At least, the
real cops, who patrol the streets.

"Many" cops also don't beat suspects. That's not a comforting standard.

Then there's the Minneapolis Police officer who arrested a permit holder for "prohibited person in possession of hollow point ammunition." Hint: he was not a prohibited person, and there are no laws against hollow points in Minnesota.