Admittedly I missed this distinction, but does the point still stand?

A BMW owner has fussier standards (on average) than a Toyota owner. The 'higher touch' a service you're trying to provide, the less welcome these interventions will be. If there's a distinction between a normal-car garage and a luxury-car garage, this probably comes down to some sort of licensing or certification from those luxury brands. Seems plausible to me that luxury brand X could stipulate things like availability of human contact points.

Re: not being a car mechanic, it's true, but I'll have you know that I replaced my own blower motor a few months ago :)