Lack of a specific time limit in GPL doesn't mean there isn't one based on what's reasonable. What they're doing it not reasonable.

> Android has always been more source-open than “open source”.

This is about Pixels rather than AOSP. Google decided Pixels would no longer be supported by AOSP which is why they stopped pushing the kernel drivers, userspace drivers and other Pixel related code to AOSP. They moved to publishing kernel driver code via Google Drive after filling out a Google Forms submission. They're handling those manually. It's a ridiculous system and comes across as them wanting to make it a hassle on purpose. Perhaps that isn't the case and someone simply needs to make the decision to simply push Git tags somewhere else. They could put it on GitHub if the goal is disassociating it from AOSP.

We accepted the archaic new system while they were responding to requests in a reasonable time but that ended. It's now very inconsistent and is regularly getting delayed for weeks or more.

> The vast majority of community contributions that make it into the codebase are security fixes and small bug fixes.

Open source does not imply anything about accepting contributions. SQLite barely takes any contributions and the same applies to many projects. There were a lot more code contributions to AOSP than you're describing prior to recent changes with Android 16. It was relatively easy to contribute to the lower level parts of it.