Android 16 QPR1 rolled out in binary-only form to phones that are blessed by Google over two months ago, and it's only just now that they bothered to actually release the source of their open-source operating system.

This means the source code is finally being released for the quarterly release that came out in september. Roms like lineageos had to target QPR0 which came out back in June but can now bring up to this. Google used to release the source to AOSP right after the releases happened, now they don't.