No they didn't..

https://discuss.grapheneos.org/d/25099-pixel-10-still-too-early-to-ask-us-when-it-will-be-supported

Our Pixel 10 support will likely only be possible to complete after we finish porting to Android 16 QPR1 which is being released in September.

They don't know IF they can even support it until they figure out the new releases that are jacking up their dev cycle.

It will be significantly more work than usual to support the new Pixel 10 phones since Android 16 removed the Pixel device trees from the Android Open Source Project. However, that was already only part of what we need for device support and we worked around it by expanding our automated tooling.

This is exactly the issue I'm referencing. Google can completely sabotage this route. We don't know yet.

Edit: I should clarify that they did say they're trying to continue, but should they not be able to crack the device tree issues they will be stuck. Nothing they released said that they've figured this issue out yet.