> but how would a company determine that at scale?

Two-way signature validation. Apple distributes unique developer IDs; make the dev sign the app locally before uploading it, like Google does for the Play Store. If those trojan horses still make it through Apple's manual inspection process, then they need to fire everyone working for the App Store and replace them with AI.

> If Apple aggressively took action against this with a high error rate

They need to take action. Apple's entire argument for an App Store monopoly is that they curate apps individually before they're uploaded to ensure a baseline of quality. When they stop vetting apps and allow the App Store to become like every other store, their argument in favor of monopoly control evaporates.

So yes, it would be anti-competitive censorship, but that's nothing Apple hasn't done before. The real issue is that their "premium" store interface is getting shown-up by the Google Play services. At the going rate there won't be anti-competitive behavior to complain about since Apple will be forced to accept competing storefronts - and they have no one to blame but themselves.