That's true, and so any thing that that company does that some rando doesn't like and claims is illegal we must assume is actually illegal, even when that rando explicitly avoids questions about what they actually think is illegal about it.
They've asked to name one law that I think Google has broken, which is already part of the public record.
If you're asking what illegal business practice Google will be engaging in when the Manifest V3 limitations will begin to be enforced: using their dominance in one industry to gain advantage and maintain dominance in another industry, to the detriment of consumers and competitors.