I just read on Wookieepedia that Darth Sidious was not the only force user to summon a force storm, and that Darth Rivan was also able to summon one through his Darkstaff. The storm supposedly transported him through time.
__________________ "The power of the dark side is an illness no true Sith would wish to be cured of" -Darth Plagueis
Freedon Nadd has also been stated to be able to summon them, and in the Tales of the Jedi Companion it's listed as a Jedi ability (while forming a distinction between Jedi and Sith abilities).
Seeing as how Sidious canonically was the first and only one to perform this feat without the use of a weapon, I fail to see how you're making any sense. Unless you're talking about an upgrade of force lightning. There's no evidence that Freedon Nadd could summon wormholes.
Also, we've been over this before and never has Sidious been stated to be the first and only person to be able to summon them. He was the first and perhaps only person to have displayed it, sure, however it's canonical fact that the technique isn't exclusive to his personal set of abilities, and that Freedon Nadd could also create them.
And in this context knowledge of the ability would correspond with the ability to use it given that it's listed under his "Special Abilities" heading, which is used in the Sourcebook to indicate what the character can actually use within the RPG. And it's not entirely reflective on gameplay either given that it also references "abilities still hidden in ancient Holocrons and tomes", which are never specified by the sourcebook and have absolutely no bearing on gameplay.
__________________ Recently Produced and Distributed Young but High-Ranking Political Figure of Royal Ancestry within the Modern American Town Affectionately Referred To as Bel-Air.
Freedon Nadd's use of Force Storms--a sketchy hypothesis at best--taken aside, it should also be noted for reference that the Complete Star Wars Encyclopedia states that Force users (Jedi I believe) have previously combined their power to conjure them.