While this is excellent snark and a great witty rejoinder to internet arguments, there is something underlying which I think is useful: Figuring it out yourself is commendable, but no-one's going to mind if you look for some expert advice from time to time.
It won't help you when exhausted, you have to get up at 3 in the morning, trip, brake a glass, open your hand and bleed on the last batch of milk. It won't help you to react to the effect of society on your child's language, choices and behavior. It won't help you with the feeling you get when you get mad and slap the child and instantly regret it.
And even for the things they talk about, RTFM doesn't make you not an imposter. Unless you practice it, theoretical knowledge has limited value.
You stop being an imposter after you had your children and are satisfied with the result.
And of course, there is no official manual, only hundred of ones contradicting each others, written by people whom expertise you can't easily assess yourself. On a topic that doesn't really have a clear way of demonstrating truth.