Noah wasn't holding back, but he didn't use all his techniques right away. He limited himself to use the warp spell and his sword arts because he didn't know what the Matriarchs had in store for him.
Cultivators were different from magical beasts. They had tricks, strategies, and inscribed items that could turn a certain victory into an overwhelming defeat instantly.
Noah was stronger than the two powerhouses, but he had to be wary of their experience and preparation. He wouldn't be surprised if they prepared items to defeat him even before the situation reached that point.
The lunges flew through the dark world without any obstruction. Noah's ability would even make them stronger if they weren't so fast.
The Matriarchs only had an instant to react, but they didn't fail to deploy spells that could stop Noah's offensive.
Great Elder Diana's crackling second skin expanded and created a spherical defensive net that destroyed anything trying to cross among its holes.