Blocking file-based installations was never planned. It's fake news and always has been. It's all about requiring code signing for all code so that malware-spreading authors can be easily blocked by adding their signing key fingerprint to the blocklist.
It doesn't matter whether the app is installed via Play Store, Huawei's or Samsung's store etc., or from APK.
This is a drastic misrepresentation of the situation. All Android apps already have code signing, you cannot install an app unless it has a signature, and any future updates are blocked unless the signature matches. This is how it's been practically since the start of Android, it's part of the security model to prevent something like a malicious Firefox APK stealing your cookies.
What's new is that they were gonna block installations outside of Google Play, unless the developer has signed up for Google Play Console and has gone through a verification process there, whitelisting their signing key fingerprint. However, they've walked back on this and said they'll create a new "advanced flow" for "advanced users" that's "designed to resist coercion" to bypass this restriction. Door in the face technique IMO, the existing 12-step process to installing an app was already complicated enough.
So effectively the result is that file based installations will be blocked unless Google has specifically whitelisted their key through the Google Play Console verification process, or the user goes through this "advanced flow" which we're yet to see any details of
I am currently in process of "verifying" my identity with Android Developer console.
In addition to proof of identity (e.g. passport/driver license) Google is demanding a proof of address, government registration, this month's rental agreement, foreign passport... The process is stuck in limbo because months-old documents are deemed "outdated", and I am constantly threatened that my verification request (!) will be denied because of "exceeding allowed number of attempts" (!!)
It shares the same principle as silent Discord account bans and other "verification" harassment schemes, such as Upwork account verification. The excess developers — Google's potential competitors — need to be banished from platform as quickly and cheaply as possible, so that Google can peddle their own spyware unimpeded.
Ask your president. I suppose republicans will soon block VPN apps, adult apps and whatever comes to their minds as non-compliant with their medieval mindset.
It doesn't matter whether the app is installed via Play Store, Huawei's or Samsung's store etc., or from APK.