If your grocery store “willfully acquired or maintained monopoly power by engaging in anticompetitive conduct”… then you’d be actively and purposefully affecting the ability for anyone to “try to build an alternative to compete with [it]”.

They aren’t asking Google to use a specific price, what they are asking is for them to stop offering special custom-made deals under the table for some of the partners with the intent of preventing competition. Nobody is stopping Google from offering the same fees to everyone indiscriminately… the issue is when they pick and choose with the purpose of minimizing/discouraging competition. Particularly when they are already the biggest one in their market by a wide margin, so they have a higher power/responsibility than a Mom’n’Pop store.