Canadian regulations use the same terminology ("flight time" - means the time from the moment an aircraft first moves under its own power for the purpose of taking off until the moment it comes to rest at the end of the flight;") and it is settled fact here that the pilot logs time from brakes off to brakes on.
Aircraft maintenance requirements are based on accumulated air time, which is wheels up to wheels down.
If you taxi out to intending to fly but return because of a mechanical issue, that's 0.2 (or whatever) in your logbook. If you taxi just to reposition the aircraft on the ground, that's not logged.