If Sukuna Actually Has Mahoraga Running In The Background, He Can't Use Any Other Technique Besides Ten

If Sukuna actually has Mahoraga running in the background, he can't use any other Technique besides Ten Shadows. But, since Dismantle is imbued into his domain by default, it doesn't require additional imput from him to use, meaning that he can have Ten Shadows and Mahoraga active. From the looks of it, it's in Megumi's pocket (shadow) dimension.

Here's some panels from his fight with Mahoraga, specifically the ones where he figures out what the wheel turn means. Its not that Sukuna has been holding back or toying with Gojo this whole time. He's letting Gojo use his techniques against Mahoraga without knowing it so that Mahoraga will be fully adapted to them! But in order to hide his hand, he couldn't use any of the other Ten Shadow abilities and having it up meant that he couldn't use his own.

We all thought he was waiting to pull Tens out, but he had it running the whole time!

That's what Gojo is seeing here.