Now that I look, I can’t find the etiquette difference between ranked/unranked anywhere in the documentation. Perhaps the only place I’ve seen it was @GreenAsJade’s post in the silly-features-that-we-won’t-get thread.
“You’re asking for a breach of a fundamental OGS prohibition: no outside assistance from bots or humans, unless agreed in advance in an unranked setting ” (for example teaching games are fine).