Keep in mind, independent stations often sell under signage of branded products. The store is still independent and a lot of them still have "shady" practices....definitely not ALL...but some do.
The big chains such as Race Track, QT, Circle K, Murphy Express, Costco, Kroger, etc DO NOT tolerate cross dropping product. The ONLY exception I ever hear of is if a higher octane accidentally gets dropped into the regular. If Regular ever gets dropped into a higher octane tank...those pumps are shut down and the tanks get pumped out whether it's all pumped into the Regular tank or onto a truck and taken elsewhere.
The big chain stores don't want the liability of mechanical issues nor violations for selling a product that does not meet the specs the consumer is paying for.