I think you're over-complicating it.
The "Doc Fee" is just another in a long line of Dealerships "tricks" and scams that allows them to falsely advertise a price on a vehicle for sale.
That's all it is.
And although states have put a limit on these "Doc Fee" numbers, it really doesn't matter what the number is.
All that matters is ... you know what the number is beforehand, so it can be factored into the Out-The-Door price.
What you don't want to happen is to arrive at the Dealership not knowing this number, thinking you're about to sign the papers on a good deal, and then "get the bomb dropped on you" in the form of a last-minute $699 "Doc Fee"!!
... and this, of course, is exactly what the Dealerships had in mind when they concocted this scam.
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It has nothing at all to do with "filling out paperwork" ... or "prepping your new car" ... or whatever other cockamamie reason the Sales Staff tells you it's for.
It's just another Dealership scam.