Comment by 0zymandiass

You've explicitly quoted that source releases are not relevant:

> or, if the source code is not publicly released, after an update of the same operating system is released by the operating system provider

They have not released the source code, but they have released an update of their operating system on their reference Pixel hardware.

Therefore, all devices must update within 4 months of that Pixel release, regardless of source drops, per this law