I've bought several vehicles with less than 10 miles on them:
'15 Silverado - the lot had 3 identical ones, I did the deal over the phone and drove to get it, it had 3 miles on it and the sales guy said it had 2 when he got in it and it flipped to 3 when he pulled it around.
'17 Miata RF - I think maybe 7 miles? I was watching for a red one to arrive at a dealer, and when it did I was there immediately.
'17 STi - It was still in transit when I made the deal, so it was already sold when it arrived to the dealer. I think it only had 3 miles on it.
'17 CX-5 - Bought for my wife, another vehicle that had just arrived and I think also was only 3 or so miles, could have been more but was definitely less than 10.
'19 JLUR and '20 Pacifica - both custom orders and both well under 10 miles. I think the JLUR might have been 5 and the pacifica about the same.
Basically, if you order you should have less than 10, especially if you're like me and tell the dealer to do minimal PDI. For the Miata, STi, and Pacifica they all came with a free tank of gas and I drove to the gas station with the sales person to fill it
However, if you're order get's flagged for extra QA before shipping, you could have quite a few miles, up to 100, when it is delivered
Years ago my mom bought a brand new Mercedes with a couple hundred test drive miles (she didn't care) and after a year or so the paint on the trunk started bubbling. When she took it in to be re-painted, the body guy told her it had been wrecked from behind pretty badly.