If, for example, Steam was going to sue developers who listed for a lower price on other platforms, to force the removal from
those other platforms, you'd have a case for Steam being abusive. But I haven't seen any case that's what happens. It's just that Steam might cancel a business relationship with a dev if the dev violates their contract. Which happens in
every business, and size is not in any way relevant. The only way size becomes relevant is that devs seek out Steam, and Steam can ask a lot and it's still worth it to the devs. But that's just business. If the developers don't like the terms, they have other options.