If they really want they will fight it and since the dealerships and manufacturers have the money they would probably win.
I keep a binder with all receipts for oil changes with date/mileage done and I make a copy of the receipt since the thermal receipts will fade. I do this for air filters, brakes, tires, rotation, install of any new/replacements parts as well. Then when I sell the vehicle I can also show the potential buyer this. People do like to see service records and it helps.
As far as warranty, luckily I've never had a vehicle in for a warranty issue that I would have to prove oil was changed.