May or may not be. It does significantly improve security.

I miss data to confirm any of this does significantly improve security.

Anecdata: I have yet to meet someone who have been targeted by unknowingly side-loading apps.

If they really want to improve security they can work on much more impactful changes. I know people having been scammed by ads proudly delivered by instagram and google. I read about malicious apps that somehow went through official store filtering.