I understand this thread received a bump, but I figured I’d leave a reply with a definitive no for you. This is not the behavior of this method. WaitForChild will return non-nil if that specific instance is prepared for access.
This is an understandable answer. Instances stream from top to bottom, → parent instance loads, child instances load, etc…
“If your game does not explicitly use WaitForChild for every instance that you need to interact with while loading then your game may encounter an issue when we modify the send order in this upcoming change .” - LordRugdumph on traditional instance replication and loading changes. Even before this modification, which I’m unsure of the current state of, this was not the behavior. You should use game.Loaded:Wait() and WaitForChild to absolutely guarantee that instances exist.