The answer is all flights except scheduled RPT should advise POB on taxi, and also when entering CTA from OCTA (if you stay in CTA, you generally don't need to advise POB because it can be obtained from the previous sector).
The reference is AIP ENR 1.1 4.3.2
Military don't have different rules to the civvies - we all play by the same rules. We just interpret them differently!
My thoughts are all aircraft should advise POB - we had a situation once where there was a MAYDAY called by a metro (smoke in cockpit) and the POB given by the company did not match the POB advised by the pilot. It was scheduled RPT.