Because CT is consistent until the user either dies or releases it.
No one knows how IT fully works. Not to mention the requirements for it is much greater than CT.
If Sasuke was completely out of chakra he would have died.
That sword isn't the size of Kurama's claw though.
Sasuke didn't even have chakra to keep three tomes, use chidori nor to stay away. Yet he can maintain his bijuu genjutsu and cts perfectly? Its pretty obviously they are not going anywhere like IT
And when we all seem to figured out how cts works, sasuke made it coreless. And when we seem to figure how genjutsu works, sasuke solo glanced all bijuu without eye contact at all(which is like IT)
So what sasuke does is not clear to us like IT, and like IT that they have been set out individually. There's no hint at all in the chapters that stated how sasuke's techniques are different than IT that it would break when the user is lost. And its plain clear that all bijuus are trapped while sasuke couldn't move and bleeding to death