Not according to World of Warcraft: Chronicle Volume III, Page 201:
Gilneas had escaped invasion from outside forces due to the massive Greymane Wall on its northern border. But that had changed with the Cataclysm. Earthquakes had shattered part of the wall, leaving Gilneas vulnearble.
Garrosh Hellscream was not the only member of the Horde who desired Gilneas. Sylvanas Windrunner was eager to bring the kingdom under her dominion. She convinced Garrosh to give her control over the invasion force, and she led the Horde’s rampage through the isolated nation.
And while you answered Julia’s question in one sense, that being Saurfang’s thoughts on Genn and Stormheim and thus the Horde motivation, you also avoided the answer to “why” the Sylvanas was attacked in Stormheim to begin with.
I do have a follow up question, if you would. Why is the Horde is holding the Alliance to standards the Horde doesn’t even hold themselves to?
In an unprovoked attack during the doomsday scenario of the Cataclysm while the world was being pulled apart, Sylvanas both tried to assassinate Genn himself - another nation’s leader much in the same way Sylvanas would be in the future as the leader of the Horde during Stormheim - and Sylvanas also broke the orders of her superiors at the time as well - as people point out that Genn broke Anduin’s orders - in both developing and deploying the Plague on Gilneas and beyond which was against the against the Horde’s laws not only under Garrosh’s reign, but also under Thrall’s before him, as the Kor’kron Overseers that had been station in the Undercity by Thrall warned Forsaken players about doing any more work on the Plague.
Sylvanas was not forgiven after the Siege of Orgrimmar just for helping out, nor was the use of the Plague any sort of secret, as Varian specifically says at the end of the conflict:
We need to investigate cleansing the plague from Gilnean lands so they can rebuild. We must contain Sylvanas.
From here on forward, the Alliance will be proactive. Never again can there be another the likes of Hellscream.
But the Horde under Vol’jin never addressed any of Sylvanas’ actions. Vol’jin never punished Sylvanas for anything she should have been held accountable for. No, instead, during Vol’jin’s rule, he actually withdrew the Kor’kron from the Undercity - once again, placed there not by Garrosh, but by Thrall - and gave Sylvanas even more freedom. Which is even more astonishing because Overseer Kraggosh was mutilated and killed during Vol’jin’s rule, and nothing was done about it, and this was flaunted in plain sight with his body openly displayed in a cage in the Undercity.
And the practically literal crowning achievement of Vol’jin’s reign on top of that? Vol’jin appointing Sylvanas Warchief. Another not just the likes of Hellscream, but worse than him, that makes him look like an amateur.
So when we look at why Sylvanas was able to launch the War of the Thorns and Saurfang’s thoughts on Genn’s actions at Stormheim that he was never punished for by the Alliance, that happened because of Sylvanas’ assassination attempt on Genn and the tactics she used at Gilneas that she was never punished for by the Horde.