You seriously couldn't be more wrong.
You're the one who is capable of defying the levels of "wrong", here. I find it ironic how the guy who thinks that Lumiya > Sidious; Revan > Luke; and Sion > Kun is acting like he's a know it all.
The passage basically confirms that when Sidious states to Luke that he has full control over his Force Storms, he was lying.
The passage basically doesn't do anything. All of a sudden, it is wrong for me to make an educated hypothesis based on the evidence we have, but you can tell me what it basically says, by interpreting it with your own bias?
No. Double standards aren't going to be applied.
In other words, Sidious knew that he didn't have full control over his Force Storms.
In specific circumstances, clearly, when a third party disrupts the process. Luke/Leia/Anakin caused the disruption that ultimately caused the Force Storm to rebound upon Palpatine. So, it was nothing that he did - but the application of ungodly power that those three generated that temporarily cut him off from the Force.
That is what caused the lack of control.
So no, you're wrong.
No, I don't see how.
When the passage states that Sidious has not fully learnt how to control his Force Storms, it means generally and not under one particular circumstance.
Does it now? Really... considering how in every other case that he used it, it worked perfectly fine? Yes, I have a hard time believing that. Especially when Luke told Leia that: he (Sidious) can't even control them completely - and they still had to cut him off from the Force.
Wanna know why? Because until something like that happens, Sidious has control over his Force Storms.
Accept it, you are wrong.
Don't see how.