Hi again f.c.
"as 20 minutes have passed, and the aircraft has not moved under it's own power, pax have a right to request to be offloaded".
I had yet another dig around some regs I have access to but I can't find that wording or rule set for general delays in Europe
, It sounds like a very quite a strongly/firmly worded PA, very much in line with much more stringent US rules....(where FWIW it's 30 minutes).
That said as you know given the rash of passenger rights legislation these days if the doors are open you're on very shaky ground trying to stop a passenger deciding not to travel the if the aircraft is doors open and at the gate.