I came across the same observation from two separate books, Ender’s Game, and The Ocean at the End of the Lane. Both child main characters are told, “Don’t worry, it won’t hurt a bit” by adults. And the MCs, immediately after, think that that is a lie, that the only times adults tell you not to worry or that something won’t hurt is exactly when you should worry or when it will hurt.
I thought it was amusing and was wondering what other interesting observations you have read. It doesn’t have to be from a wise child MC talking about adults, but it could be.