Earlier quoted context omitted.
1) The one-time, one-day waiting period only applies if you go through the advanced flow to allow installing unregistered apps. You can still install registered apps (ie. apps made by developers who have verified their identity) even if they're distributed outside the Play Store. 2) You can use ADB to immediately install unregistered apps. ADB installs are not subject to the waiting period.
So let's say I'm F-Droid, an organization making a direct competitor to the Google Play Store and openly pointing out how much scammy shit is available in that store. My options are 1) submit my identity to Google (my competitor) so they can identify me and choose to revoke that verification at any point, or 2) I can tell all my users that they must go through these scary dialogs AND wait 1 day before they can use my…
You'd think regulators should make Google ship a 'Choose my store(s)' screen at setup, but Google thinks the opposite is the case and Google should also be able to control app distribution outside of the Playstore.