No, its not true. But it can be a usefull advice to beginners who tend to play these moves when they should concentrate on development and influence in the centre.
Kadas opening
It's not written in stone, but useful advice to get you started. A move like ...h6 in an innocent looking open game may already lose.

I've played against Kadas twice and both times it's like what are you doing. I'm in no way a chess God but I know enough to play the center and use your A/B pawns and G/H pawns for blocking and counter attacks.
As a beginner player I have been watching videos. IM John Bartholomew was saying not to move your A pawn or H pawn unless it's necessary. If that's true why are there openings like Kadas then?
It's not there because it's any good. It just conforms to the rules, so it exists. If it exists, someone will play it and plug a label on it.
I didn't even know that it has a name.
As a beginner player I have been watching videos. IM John Bartholomew was saying not to move your A pawn or H pawn unless it's necessary. If that's true why are there openings like Kadas then?