He said he needed patches to make the GPUs work. Kernel package auto-updated does not have those patches and overwrites the custom kernel he built every time there was an update available.

I presumed that as a kernel developer, he would run the kernel he runs, which would require rebuilding periodically. Daily doesn't make sense, monthly is too infrequent given the rate of change in the kernel.

My speculation though. When I was building an app I was using, I used to run a recent stable build on my device instead of just the one released in the Play Store. Simplifies having to keep multiple devices.