Myths and Misconceptions abound relating to powder skiing.
Like: You have to sit back, you have to push yourself out of the turn, you have to swing your upper body, these are only a few.
In reality, if you learn to manage your ski to ski pressure as needed, which is constantly changing, you will already be 50% more successful. I try to begin my new turn, by finding outside ski balance, with my skis close together. Once I find my balance; I can go 70/30 distribution. But if you try to be 50/50 all the time or 90/10 all the time, it will never happen. You need to be constantly adjusting, always.
Bottom line if you are losing your outside ski balance or one footed outside ski skiing on groomers, it will get worst in powder. Again, you can take this statement to the bank.
Powder is more difficult for most skiers, if you are not skiing in balance or not on the outside ski on groomers. If your stance is wide on groomers, that won't work in powder. If you don't tip and release off your big toe edged ski, first, to release, you won't ski powder well. I can go on and on, but this is all basic PMTS.
It's definitely not taught this way with Traditional Instruction. They want you to huck your upper body, extend or push off and twist your legs, have fun with that!
I find skiing powder easier, why? Because my balance is on the outside ski and I can keep it there through every arc. Leaning, rotating and sitting, doesn't work in powder, any better than it does on ice.