Why didn't Sukuna transform and then use WCS against Gojo?

Factually, it doesn't even take a second for Sukuna to transform; we've seen this against Kashimo. Sukuna transformed when Kashimo's lightning was inches away from hitting him. So why didn't Sukuna transform when he was coming out of the rubble or when he was under the rubble? 

Gojo, after regaining his RCT, might have also regained his domain at some point after hitting four black flashes. 

But using domain expansion while Mahoraga was out would have been a bad idea, as Mahoraga could pretty much instantly break it, and Gojo wouldn't have been able to one-shot Mahoraga with red to prevent him from breaking the domain.   However, once Mahoraga was exorcised by purple, there was nothing really stopping him from opening unlimited void.

Note : If Sukuna regains his domain in the next few chapters, then Gojo surely had his domain at that time. Even Yuta was worried that if Sukuna gets his RCT back, he'd get back his domain too.

Furthermore, If Sukuna had transformed he'd still be fighting at 12-15F worth of strength compared to Gojo who had gotten back his CE and RCT output back. For those confused, after Fighting Gojo, Sukuna had lost half of his CE reserves and was suffering from low CE output. Lower CE output means that the CE reinforcement will be weaker, so the user will be slower, weaker, less durable, etc.

Essentially, Sukuna's Hein-era incarnation would have to face Gojo, who not only has his domain back, but is also physically faster than Sukuna due to his restored CE output. Assuming Sukuna had transformed, Gojo would be on guard, opening the domain instantly and killing him as soon as possible, which is why Sukuna was forced (according to the narrator) to create a BV.

That's my take on this...what are your reasons on why didn't Sukuna transformed to use WCS.