Generally speaking, swirls are evenly distributed across the paint of a vehicle. What you’re describing would result in Rids not swirls because a pebble or 2 would result in isolated scratches not evenly swirled paint.
Swirls across an entire vehicle can happen after just 1 improper wash & dry. I’ve seen it, heck I’ve done it and I’m pretty sure everyone else here has as well at 1 time or another especially when dealing with soft paint.
I’m not saying it’s common to result in tons of swirls after just 1 wash, but if the wash method isn’t great there will be some after 1 wash.
The point is if the rest of the vehicles in their showroom have swirls you can count his new car will as well after 1 of their washes. But that’s not to say there isn’t competent dealers nowadays with guys who know what they’re doing.