Quote Originally Posted by Faafetai View Post
Though I am unsure where to see what instance you are on currently when first logging in, but I am sure I will figure it out eventually.
FWIW, you can do /instance in the chat-box to see which instance you are currently in.

(As others have already mentioned, it wasn't in any patch notes because it's been a thing for ages when a zone would otherwise be unusable due to congestion; it's not a new feature. You are not wrong that it is, however, not a well-documented feature if you don't already know it's there.)