If this is a thing then the solution they offer is incorrect. A big giant red screen: “warning the identity of this application developer has not been verified and this could be an application stealing your data, etc” would have worked. What they want is to get rid of apps like YouTube Vanced that are making them lose money (and other Play Store apps)
"Displaying an angry warning message" is one of the tools we've used for decades, and never with much success.
Plus, you are not required to do that, you can just stick to Google Play and trust what Google approves there. But no need to lock down others because of your recklessness.