In previous quarters you'd be lucky if it was washed at all before handover, mine was filthy upon collection and covered in little bits of some form of protective wrap they used for shipping, complete with sand from the Mojave.
Usually I'd say not to be concerned, but some of the pictures I've seen from the last few days do look like Tesla have made an effort to prep the cars before handover.
Your detailer may well be assuming the new show room shine of a new BMW/Merc/Audi will also apply to the Tesla, which isn't going to happen when there are 500 of them in a car park, all going out that week. I don't think he should have anything to worry about, and ultimately as part of the paint correction they should have the kit to strip the polish back if necessary.
My preference would be to collect a clean car, that way you can see clearer and report any issues with the paintwork that are beyond what a detailer would be able to correct.
This makes a lot of sense! Thank you so much @Medved_77