I feel the title editorializes a bit too much. The thread only confirms the bug, not a specific cause yet. As sibling comments indicate, the effect on GrapheneOS users is undetermined.

This is standart, and happens constantly with Invidious (youtube frontend). This happened before on AuroraOSS too. They probably just flagged the accounts and no API change or A/B testing an API change.

This also has nothing to do with GrapheneOS except for some user overlap.

For me, the issue also only occurs sometimes. Usually I can download apps like normal.