Not so. The new mandate isn't that all APKs must be uploaded anywhere, only that all APKs must be signed by approved developer keys. So to test new builds, devs will only have to sign with their approved key, then upload. No extra hassle once you already have an approved key.
I'm not sure it works that way. _In general_ before the recent announcement you are supposed to sign the debug build (what you feed into adb to install) with your debug key that's different from the release nor upload key, and the debug key is never submitted to google.
Of course _maybe_ at some point google will also force you to submit your debug key to them. But I don't believe that's the case now.