Generalizations usually do.
Simple truth of the matter is that shotgun training in aggregate in LE is minimal at best. (In several departments I can name, it is outright non-existent) There are certainly pockets of competence and even excellence which is why I made specific reference to organizations like the ones in SOCAL who have done a lot of gunfighting taking shotgun training and deployment seriously. USBP has also taken the pains to maintain excellent shotgun training over the years and USBP guys I've talked to are big fans of what the weapon can do.
Organizations that shoot a lot of people with pistols pretty quickly figure out that pistols suck.
I mentioned that, too. Of course, most police departments are not running guns set up to really use slugs to their full potential and the departments that never really invested the time and effort into figuring out what the shotgun can really do for them are likely to be using soft lead foster slugs (that likely haven't really been tested thoroughly in each issued shotgun) which give somewhat less than optimal performance in and around vehicles compared with the performance of some of the better slugs for the task like Brenneke or Federal's recent TruBall deep penetrator slugs.Also......slugs. Sorry, but if you work in an automotive based world, you are doing yourself a huge disservice in not knowing how to effectively utilize the best tool we have for dealing with felons in vehicles.