Exactly. It would be complicated to pull off something like this via side loading given that Apple’s proposal requires apps to be hosted on an alternative store rather than just being a single app that you could download (like APKs on Android). The paragraph below from their Newsroom post about the changes being made also suggests there will still be some form of app review happening for apps even if they aren’t being hosted on the App Store.

Notarization for iOS apps — a baseline review that applies to all apps, regardless of their distribution channel, focused on platform integrity and protecting users. Notarization involves a combination of automated checks and human review.

It would be easier for a scammer to use an MDM profile like they did with this scam rather than trying to trick people into side loading.