They were not really vague. Leaving a bricked key is not griefing, being forced to bang your head against an impassable wall would be getting griefed. They clearly stated that players who were banned were intentionally griefing consistently.
I ran a few M+ this morning (my 9 millionth ara kara run for trink) and only had to leave 1 because they couldn’t kill last boss. Not my fault 