There is no ICAO requirement to be within 30 degrees of the centreline,
Being an old fart, with depleted memory and a joy of basic flying, I remember an old edict that a circling approach was any approach where the approach track was >30 degrees from runway centreline. Thus, once within 30 degrees you were no longer circling and descent was at pilot discretion.
Our A330 FCOM simply states the following:
"MDA/DA shall not be set in the FCU ALT window."
No explanation is provided in the FCOM or FCTM and there doesn't appear to be any latitude when it comes to circling approaches. I don't know the reasoning behind the ban;
That to me is scary and indicative of todays pilots. (no offence to the individual). You receive an instruction that seems odd and you don't understand and you don't ask WHY. I've flown for various airlines and come across plainly daft/unnecessary SOP's. I asked the question, Why this and Not that?. No reply, just a blank gaze. As the operator gained more experience on the a/c the SOP's changed to guess what........
Why do pilots not question more, but just become sheep? They are the frontline guys not the desk jockeys. I once flew for a fast expanding airline where the CP lost his type rain for not flying the line, yet he was writing the SOP's. Give me strength.