You can only use 5.15 on Pixel 8 and later at the moment. The 6.10 builds are because Google is planning to upgrade to Kernel 6.1 for all Tensor devices in the future. When an upgrade is done above, we will follow.
Discussion
kernel 6 has been pushed on all the desktop systems for about a year now but it's a bag of expletive, only starting to get stable now
i had huge problems with the AMDGPU drivers especially