All well and good Defred, except of course a professional aviator will have anticipated the change in holding times you describe and should already have that plan B up their sleeve.
Never had a “Mayday Fuel” to cope with, but most definitely have called “minimum fuel” a few times...as the intent is to communicate to ATC my actual fuel state, if they subsequently ignore that..well as Don says..they can deal with a Mayday if based on the company fuel policy and state of operator regulations.
I have however committed to landing my destination a number of times (which is a whole other can of worms)
Quite right that ATC aren’t there to reward minimum fuel carriage, but at the same time I need them to work for me.