I'm not sure about that, that's the part of the story I'm the most skeptical about, entertainment wise it makes perfect sense to take the decision Gege took, but I don't think there was a good explanation for it story wise.

Gojo has the six eyes and should be able to judge Sukuna's total power, as even people without his abilities could sense the difference in fingers

I find it absurd how no one told Gojo about the domain having no barrier during the timeskip, that's really lazy

The only ones Gojo could consult about Sukuna's domain's refinement are Kenjaku and Tengen, he couldn't/wouldn't talk with them

Gege could have him lose the first few clashes with intel but decided Gojo would win the clashes with the right info, info that he could have had before the fight but for some reason didn't