vagymmomma
Proud Parent
If you are talking about gateway skills, I would include twisting. Half, full one and a half, double, triple; front or back. Similar to a kip some kids seem to learn to twist easily and others take a while, but once they get it they've got it. It is difficult to add much variety to floor passes or dismounts or vaults without twisting.
I debated whether to put down twisting. The reason I didn't is that (in my limited experience) I never found twisting to be the reason that a gymnast tapped out. And it took my DD a long while to figure out her full (if 6 months is a long time in this world), but it boiled down to a mechanical issue that once identified was quickly corrected.
Twisting is certainly easier for some girls than others (especially those fast twitch types when doing doubles), but those with good tumbling, good coaching and the right equipment are more likely to find their way through. In contrast, kips have been a major roadblock even with privates, weight training, and years of practice for some girls. Part of it is strength but I think some girl are just naturally better swingers on bars.