I thought BA only performs op-ups and has no complimentary upgrade program like CO's UDU for Elites, so it's rather hard to compare, no?

flying non-rev with BA in the 1980s & 90s (father retired Capt) some staff tickets had J or F entitlement (yes - that was the terminology used ) and if there was no revenue pax booked, seat assignment would be in J or F ahead of FF upgrades and, frequently, op-ups - not shenanigans; just the way the staff-travel policy worked at the time

of course this info may be really out of date, but if correct seat assignment didn't happen at the gate or in T3 and T4 staff travel dungeon then the final word was with the CSD onboard after boarding - and that WAS shenanigans hell, let me tell you

Frequently junior stewardess #12's ID-90 boyfriend in F ahead of Capt on F-entitlement annual concession ticket.

then again, I think there is a measure of culture: British sense of fairplay - propensity to form orderly queues, etc.