Why not? They could have kernel accommodation for one feature, and user-land leakage for another.
Also, for some features you need both kernel and userland cooperation. Just think of eg fuse or io_uring or mmap that are in the public kernel. You can surely imagine that Google might brew up similar features.
(I used to work at Google. But I didn't have any special insider knowledge about their kernel stuff. Which is good, so I can't violate any lingering NDAs here with my speculation..)
> Those patches implement various internal APIs (e.g. for Google Fibers), provide hardware support, add performance optimizations, and contain other "tweaks that are needed to run binaries that we use at Google".
I'd assume if you're making allowances for custom-made processors at the kernel level you wouldn't also want that leaking into your user land binaries as well.