On stock Pixel firmware and on Samsung's variant of Android, when removing earbuds with in ear detection turned on, the phone will pause and then also change the default audio route to speaker.
On GrapheneOS using a Pixel 10 Pro XL, the behavior I'm experiencing is only pausing media. The default audio route stays routed to the removed earbuds.
It seems reasonable that if the buds don't detect being in an ear that they should not remain the default for outputting audio regardless of being connected via bluetooth, so I assume this is some sort of regression. I'll test Lineage OS's default behaviour when I get my spare pixel 7 back.
I've tested using Pixel Buds A Series and AirPod Pro 2 and they both reroute audio as expected on stock Pixel OS and my old Note 9. Hopefully there's just some toggle I'm missing?