(Tedious disclaimer: not speaking for anybody else, my opinion only, etc. I'm an SRE at Google.)
> But doesn't Google tries to avoid GPL?
No.
> I think they're pretty anti-GPL with Android, and have some rules against inclusion of GPLed components there, besides the kernel.
OEMs don't want their hardware support to be GPL-encumbered. See https://source.android.com/source/licenses.html