Whilst regular delays I believe no, it shouldn't affect boarding groups.
The one exception I want to ask (and experienced on Sunday night) was last flight out of MEL bound for SYD. Racing to make curfew due to the delay (aircraft arrived at 20:50 original departure of 21:00). They chose to start boarding group 4/5 (middle of the plane) at the same time as group 1/2 and asked people to try and expedite everything if possible.
Just for reference, they were preparing all pax for boarding before they could start (form line groups here, here etc) and were trying to expedite everything. Pushed everyone from the lounge 10mins before boarding could even start. I don't think I've seen QF try to be this organised before a flight to get everyone onboard and leave asap.
Yeah - thanks to the SYD curfew being a hard stop to operations, having an aircraft and crew out of position at the end of the day is a massive pain for airlines and probably quite expensive as well (i.e., crewing and passenger accommodation).
Given all the padding built into the schedules now, it's still pretty embarrassing that domestic airlines can't operate to a schedule as the day goes on. It definitely feels like priority boarding goes out the window once the aircraft is running late, and the later in the day it is, the less likely that priority boarding will be done, or done half-coughd, or not done at all.
At the moment, the difference is that Qantas ground agents have very little leeway for varying group boarding as it's implemented by default at larger airports (maybe all airports?) with the "computer says no" programmed at the boarding gate, whereas Virgin may have gone from having very strict and proactive enforcement pre-Covid, to poor or sometimes no enforcement of priority boarding now (although I don't fly with them as often so open to others opinions who do fly with them more frequently).
It would be interesting to hear from air crew and ground crew at both airlines to see what metrics are being measured, and what is being punished or rewarded. I would expect the metric of turnaround times and on-schedule departures to be more likely as measurable KPI's that are monitored by management rather than the implementation of priority boarding, so its totally unsurprising that priority boarding goes out the window if there was fog in Melbourne, an ATC called in sick or a shower of rain in Sydney earlier in the day, which is all it takes to throw airline schedules into chaos.
www.australianfrequentflyer.com.au
