Here is a partial answer:
F1 Sporting Regulations
172) After receiving the end-of-race signal all cars must proceed on the circuit directly to the post
race parc fermé without stopping, without receiving any object whatsoever and without any
assistance (except that of the marshals if necessary).
Any classified car which cannot reach the post race parc fermé under its own power will be
placed under the exclusive control of the marshals who will take the car to the parc fermé.
Well during a donut you are technically stoped because you are circuling around in the same place....the distance to the Parc Fermé stays literally the same for the period of time you are donuting!