Strate and Level - that is your opinion only, not CAA policy as you well know.
If you really want to be picky, what would happen if you authorised a student to fly 2 visual circuits. Then taxy in, stop, get a quick cockpit re-brief and re-auth, then taxy out for a second session of 2 visual circuits.....then another.....and another.... 25 authorisations would come fairly quickly that way!
Flight time is from 'the moment at which the ac commences taxying with the intention of taking-off until the moment it ceases normal taxying after landing. Hence by the Eurocracy which even you at the SRG can't deny, 3 legs are 3 flights. Each flight requires specific authorisation; so that's 3 authorisations.....
MJ - such a FAQ would require someone at the CAA to come up with policy. That would need legal backing to have any substance - so you'll probably get the usual sloping of shoulders until someone at the Belgrano takes the bull by the horns and says "You'll do it this way because I bŁoody well say so!".