This does not mean that Google is making Android a closed-source platform, but rather that the open-source aspect will only be released when a new branch is released to AOSP with those changes, including when new full versions or maintenance releases are finished.
It seems like the particular news does not mean android is increasingly going closed-source, just that the dev branch will be private. Is there an evidence that they are taking components out of AOSP?
As a user, I can definitely say that GrapheneOS is the single best project in the open source space. 99.99% of stuff works out-of-the-box, with de-facto feature parity. The remaining 0.01% is the one dumb investing app which I can only assume has sneaky spyware on it.
I never get people saying that apple is actively spying on you without giving a real evidence, when that is not where their profit lies. Honestly, it comes off as being paranoid.