About as sure as I am that all pumps labeled "Premium" actually dispense 93 octance premium instead of the mid grade. There are mistakes made every day, and there are purposeful "mistakes" made as well.
Jerry
I can't speak for all gas stations but one that I do maintenance on, they have all three fuels...Reg..Mid...Super Unleaded. To get Mid grade Reg and Super are mixed in the piping and dispensed at the pump. The valves can be calibrated for either 92 or 93 octane. They run 93 because of the outboard boat motors.
They tell me that in order to carry non ethanol fuel it costs them an extra .05 gallon and they can only receive fuel when a full tanker can be delivered to their area.