Several people suggested that his illusions were different this time since he had fused with his sword and therefore had no control over them, but this does not explain how Aizen was employing numerous illusions at the same time. Please accept my apologies for the length of this message. But, with the book becoming hurried, it's possible that Kubo meant to depict Aizen's bankai, but due to time constraints, he had to make it enigmatic and up to interpretation.
Let's take a look at how Yhwack was vanquished...
Yhwack, even with the Almighty and the Power of the Spirit King, he would have been killed by a single swing of Bankai Ichigo, who wasn't even utilizing his Hollowfied abilities and was injured. His Almighty ability rescued him, making him the most haxed character in this comic.
Aizen personally fought Staark, Baraggan, and Halibel to put a stop to the opposition's resistance. He was about to expose Ichigos' ancestry when Isshin interfered and took over the battle. After the battle, he was able to absorb the Hogyoku and transform into a Hollow. Ichigo's hubris also plays a role in the series' conclusion. He is the 5th Division's captain and a tough combatant. His kidou allowed him to use a razor-sharp knife to stab Ichigo. The blade also allowed light to enter the roof, forcing it to collapse.
That was there to hype it up. Uqluiorra's experience may have been similar to how Aizen's chrysalis experience was beyond the grasp of others. Kubo didn't simply put the line in there for no purpose; it was to indicate it was on a different playing field, and he stated "not only is it larger or stronger," implying it was likely bigger and stronger as well, but it wasn't the only thing that terrified him. And since Aizen had prepared all of Ichigo's bouts, including Ulquiorra vs. Ichigo, he had to be aware of his second release.
