It doesn’t. The closest thing to the ToS that it falls under is "The Terms of Service also promote “sportsmanship and good behavior.” But it doesn’t specifically say you have to always rezz when its available. So if I need a couple breaks here and there, there is nothing you can do about it hall monitor 
It’s under avoidance buddy.
Link the ToS that specifically mentions ghost form in battlegrounds, i’ll wait. It’s not against ToS to have to take a bathroom break.
Here you go.
- Your use of the Platform to interact with Blizzard and other players is governed by Blizzard’s Code(s) of Conduct (the “Codes of Conduct”) and in-game policies (the “In-game Policies”). The Codes of Conduct and In-Game Policies are not meant to be exhaustive. The Codes of Conduct and In-Game Policies are incorporated into this Agreement by this reference, and are available on Blizzard’s Customer Support database, located here. Please note that violation of any of Blizzard’s Codes of Conduct (including with regard to Your use of Blizzard’s Websites and Forums) may result in penalties against your Battle.net Account, including suspension and/or termination of Game licenses.