Usually, yes. But not always. 10.12.6 was working until July 1st, when the WoW patch that day abruptly cut it off. This was almost certainly due to Blizzard using the most up to date XCode in order to support the latest Macs properly. There is the potential for 10.13.6 to also be cut off if Apple decides to be douchebags and make XCode not target 10.13.6 before WoW 10.0 launches.
I’m still on 10.13.6 because I can’t go further, being that I have a GTX 1080 Ti for my GPU. I want one of the new AMD 6900XTs, but I can’t find it for any reasonable price or I’d get it so I could update to Big Sur and be done with the OS hassle for another two or three years.
You can do something to mitigate the OS nag slightly. Open Terminal, then copy and paste the following line into it and hit Enter:
defaults write com.blizzard.worldofwarcraft DisableOSVersionCheck YES
You will still get the OS nag once, and continue to see the ! triangle on the character select screen letting you “know” your graphics drivers are out of date (duh), but you should no longer get the popup on starting WoW. This will only allow WoW to work for you as long as the version of XCode Blizzard is forced to use also allows targeting 10.13.6 as a minimum OS. Our days on that OS are numbered, unfortunately.