Seen elsewhere that these flights are indeed bulk loaded, and can take 12 hours to offload. Don’t know the size of the crew, but you’re talking a significant chunk of a handling agent’s manpower dedicated to work the flight at a time when they are desperately short of staff. Frustrating, but it would be madness for them to take it on at a time when shortages are only likely to get worse in the short term. Getting in a load of zero hours people at short notice is all well and good in theory, but remember they will need ramp access, hence security clearance, which isn’t a 5 minute job these days either, and presumably adds to the cost.
Show me a business that says yes to every demand, and I’ll show you one that will have folded before long!