Google says that only apps with verified identities will be installable on certified Android devices, which is virtually every Android-based device—if it has Google services on it, it’s a certified device. If you have a non-Google build of Android on your phone, none of this applies. However, that’s a vanishingly small fraction of the Android ecosystem outside of China.
Which does suggest that it applies to everyone, as opposed to being something that only applies to Play Protect.
The article has this to say about it:
Which does suggest that it applies to everyone, as opposed to being something that only applies to Play Protect.