top tier and additive blending
it is probably not the same since the fuel is transported by pipeline, then truck transport. An additive package is then poured into the transport trailer compartment and allowed to mix as the gas is hauled to your local retailer. It however is close. you got to trust someone sooner or later.
Quality gasolines have the additives blended at the truck loading rack into the gasoline (or diesel) stream as it is being loaded into the truck. It's a metered amount that varies by gasoline (or diesel) brand. Gasoline (or diesel quality is regularly tested by taking samples from the gas station pumps. If it does not meet specifications, which include many parameters along with additive type and quantity, the supply chain is investigated to determine why and to take corrective action.
Top Tier gasolines (or diesel fuels) have the same additive metered in the same amounts anywhere the gasoline is loaded and subsequently sold. They generally have more than the minimum amount of additive required by law. If someone is dumping it in the truck loading compartments and hoping that sloshing it around while in transport will evenly distribute the additive, then it ain't top tier, it likely won't be evenly distributed throughout the truckload and who knows what you get.
Some people eat fatty foods every day and they don't drop dead. However, looking into their internals might show deposits that may one day kill them.
Yous pay your money and yous take your chances. it's OK. It's your money.
