Personally I don't think a pilot or any other crew member being on UK soil for the sole purpose of an aircraft turnaround is going to be affected by this. The examples given in the document seem to indicate that the arrival and departure days are countable when they are wrapped around whole days.
Furthermore, if you don't get off the aircraft then how exactly will HMRC know you've been on UK soil? apart from checking rosters of course, but I doubt they'll be doing that.