Besides the report says, "Final Reserve Fuel being the minimum amount of fuel with which pilots should plan to land."
If you happen to go below that FRF unplanned, isn't that what it's actually for?
NO! Absolutely NOT!
FRF or MLA Fuel is "Must Land Now" Fuel Level.
Your 20 Minute Reserve Fuel or 30 Minute (or whatever amounts you use for Day/Night) Reserve Fuel Level is that which you can use for unplanned delays.
The Minimum In-Flight Level is there so Dumb Asses do not run the aircraft completely out of Fuel. That is the result of far too many Pilots trying to get back to the Fuel Pump despite knowing they are really cutting it close.