If he flew it to expedite the flight to get to your part of the lesson, I'd get it. But and without overloading a student, you should be hands on at every component part of the lesson. Taxiing included.
For what it's worth as a 737 Captain, I still see this behaviour even now, when it comes to letting the F/O brake on landing to a taxi speed as per SOP's. My bugbear with this is that F/O will never learn to use the brakes if the Captain keeps taking control at say 80 knots. Same thing, just bigger
