Google Play system updates are a thing since the first Pixel, and still continues to be updated to this day. So there still is some form of system updates.
Samsung S7 (same year as the first Pixel) when it reached end-of-service had to have a few security updates due to some pretty big android exploits. Pixel however did not need a security update because Play system took care of it. So even though your Pixel reached EoS, it actually didn't really.