New updates for older watches?

Hi, I have an apple watch series 2 and it has been running Watch OS 6.3 for quite a while. With the new security updates for iphones and watches this week I was hoping it might get a new update. It looks like the info on these updates only lists watch series 4 and newer. For others with series 2 or similar, what is the newest iOS you have been able to pair with?

I kept my iphone 6s that is running iOS 15.1 and don't use it as my everyday phone, just keep it like an ipod to keep the watch active.

From what I understand, if I allow the phone to update to a newer operating system it will not be compatible with the watch anymore.

Does anyone have any experience using these watches with a phone running a newer operating system?