I haven't seen this tactic used in Florida YET, but BOLO for it: last time I went through DTW, there was a tidy small sign on the checkout booth that said that if the odometer showed you did not drive more than 75 miles, you would be charged a flat rate of $14 to refill the tank, UNLESS you presented a same-day receipt upon vehicle return showing a purchase to fill the tank.
That was a new one on me. Wouldn't surprise me at all to see it pop up at MCO, where so many people only drive back and forth from off-site lodging to the theme parks.
FWIW, we usually top off the tank at the Speedway on Epcot Center Drive just before it runs into 417 (just east of Caribe Royale.) That one is 16.9 miles from MCO
If you really are concerned with being able to show an under-10-mile receipt, one of the best options is to drive THROUGH MCO and out the North Exit, going northbound on Semoran. If you take a left on Lee Vista Blvd, there is a WaWa there that is the closest station to the airport that never gouges on price. (There is a Panera across the side street from it as well, should you want to pick up a good meal to go for the flight.) Distance from that station back to MCO is 3.9 miles.