Peter, it says quite clearly it's calculated based upon the GW AT TRANSITION to the Approach phase. I've had several trainers in the biggest Airbus operator in Europe, second biggest in the world also tell me it. When you go around or touch and go everyone knows, or will find out, that you need to RE-ACTIVATE the approach phase. Clearly you're such an ace you've never gone around.
I however have done my fair share and know you need the 'As': activate approach phase, autobrake, approach checklist. With an activate secondary thrown in at the start of that for an immediate return. Trust me.
Worth also noting that if you go to headings I.e. are RVd for an approach prior to approach phase activation (be it manual or automatic at the D point) as is the case on 90% of approaches then you'll need to activate it yourself or you'll get the pain in the ar$e situation described above.