That's not really a thing, but even if it was, it would still not be frontrunning. Order flow is purchased for the specific purpose of making a market with the wider bid-ask spread acceptable to retail investors. They tend to place market orders and don't particularly care if their trade is off by a cent or two.

You can quibble with the academic arguments on whether or not this facilitates liquidity and price discovery (and therefore helps retail investors). Or you can just place a limit order and move on. Either way, nothing illegal or nefarious is happening. Just because they're purchasing order flow and executing your trade doesn't mean the national best bid and offer (NBBO) is being violated.