Top tier fuel is called that for a reason. The fuel at your local Shell station is not the same as x?x? brand, Valero isn't the same as BJ's or Costco. Most of the fuels that are not top tier do come from a single distributor for a region, sometimes even the others do but they're in separate tanks and often use different delivery companies. They can't all advertise different additives, mixes and chemistry and then sell the same thing, there are laws about that...
https://toptiergas.com/FAQConsumer/ Go down the list of questions, some touch on how the rating works and how fuels from the same truck can be different for different companies and some formulations are different from one company to the next.