“In violation of GPL” is a stretch. Can’t imagine Google is making the process of obtaining source code easier on themselves though. Android has always been more source-open than “open source”. The vast majority of community contributions that make it into the codebase are security fixes and small bug fixes. Everything else is essentially all the work of Google and (to some extent) Samsung.
I believe this isn't actually about "Android" at all but rather Pixel. Android is still openly accessible on git. But the kernel sources for Pixel devices is now behind this big song & dance for some fucking inexcusable reason.