I asked a gm about this and that is considered manual. I also multibox in this fashion, record it, and send it to blizzard to report bots their hacks email.
“If all the moves are performed by you manually, then there is no issue with that. If you have other characters on follow, but during the fight you manually switch between the windows and manually cast spells - that is ok. Hope that helps!”- GM response (GM named censored for privacy reasons)
If you read the tos it’s all about mirroring and software use. It’s simple. Do not use hardware to mirror your keys, and play manually.
Edit: and software don’t forget about software. More specifically third party sofware. An OS is a requirement of wow to play (be it mac or windows 10). I think mac has a form of round robin that if you hit the key it goes to the next window but I’m not sure. Honestly never met someone that multiboxed on a Mac.