Series 8 Apple Watch will be recognized as an Series 6. Unlocking does not work

Mine did something funky like that too. So, I renamed the new watch which was named, "Jeff's Apple Watch 8" to, "Jeff's Watch 8". When I did that the words in the parenthesis disappeared, which is fine with me. My old Watch 5 still shows up in that window and I have not had any luck figuring out how to remove it.

I've had the same issue (Watch identified as 6 instead of 8 and impossible to 'tick the box regardless'). I renamed the watch on my phone, had to restart the MacBook and then it did show up - as the name I created (indeed the 'Series 6/8' info in brackets disappeared, but well, at least now I can unlock it with my watch!