Android is attempting to discourage good / regular users from sideloading apps, rooting their phone, etc.

Android wants good / regular users to pass things like Play Integrity with the strongest verdicts.

This helps app distributors to separate regular good users from custom clients, API scripting etc that is often used to coordinate scamming, create bots, etc. If an app developer can just toss anyone who doesn't pass Play Integrity checks in the trash, they can increase friction for malicious developers.

Play Integrity and developer options are entirely separate as far as I know.