Yup, Sukuna's range allowed for this to happen.
And yeah, Gege is either a huge idiot and made Yuji and Co not tell Gojo about the domain. Or Gojo has a plan.
I doubt the second part is true imo. Gege probably just didn't give a fuck to be consistent and is rushing through the fight
Choso: "From what Yuji and Inumaki have said, I don't think Sukuna's domain closes off a barrier"
Everybody else: *Say it's impossible*
They must have told Gojo, but the later may have been skeptical about that possibility, as anyone else were this chapter, even Kashimo and Yuta.
When Gojo explained DE to Yuji, he never mentionned berrier-less domains. So he may have never heard about it before, and thus doubted about such a literally impossible feat.
This is maybe why he was shocked in the last chapter: he insta understood what happened: it is possible.
This is also maybe why he used his DE this soon: to check if it was true, and if yes how it works.
Cause with the 6th eye he can now replicate it.