I don't think the FAs know who paid what (including who is on a reward) but they do know status. And any gate upgrade including opups (and SEs) will be noted as ML*1. That strictly means that you only get a meal if it is available, but the FA would likely decide how to go about it knowing the pax/meal numbers.

I am sure it has come up on other threads, but codes go from ML*1 to at least ML*5. I have no idea what the rest of these codes indicate (although I gather that staff may be coded in some way).