What Uruame said has nothing to do with Yuji being more resistant to Sukuna's slashes than others. Her statement is concerning Yuji's relative potential in comparison to Sukuna's. She recognizes him as different but related to Sukuna, not as Sukuna. Shoko's statement says Yuji has essentially been made into a cursed object of Sukuna's, but a cursed object of Sukuna's isn't Sukuna himself.
Then read it again. If Yuji's CE signature isn't identical to Sukuna's, then Uraume wouldn't even be able to pick up on Sukuna's CE residuals. That's also why Shoko says Yuji is like a cursed object known as 'Sukuna' in the first place—it's because of Sukuna's CE signature. The point isn't to prove that Yuji is literally Sukuna, but that Yuji retains elements of him.
By the way, Sukuna is a cursed object—he’s literally classified as one.
Those scans have nothing to do with why resonance wouldn't occur. The reason why I bring up resonance not occuring is because it points towards Yuji's status as a cursed object being strange and not that strong. The influence of Sukuna's CE directly appears weak at best and non-existent at worse by the point Yuji is in the series.
You clearly haven't read any of the scans. The requirements for resonance remains vague, but it's most likely that minor physical changes and exchanged information alone can't cause Sukuna and Yuji to resonate. After all, Sukuna wasn’t informed about any of their plans, nor was he aware of Yuji’s missing finger that Yuta fed to Rika.
Yuji isn’t a cursed object either. Not sure from where any of these ideas are coming from.
Also, as I've already laid out, even if resonance never occured it still wouldn't have anything to do with the fact that Yuji's CE signature is like that of Sukuna's.
And my point is, if Yuji was truly uniquely tougher against Sukuna's CT because of him being steeped in Sukuna's CE then that would be pointed out. We have folks like Kenjaku, just casually dropping how their is no poisonous effect for him to suffer against Choso's blood, Gojo himself mentioning why he suffered less damage, and people randomly commenting on Sukuna's ability to double jump. If this was truly something at play in the final fight, then it would be a detail mentioned by anyone. A random small detail like that not being brought up when random details are constantly mentioned feels like this isn't really something at play in the story.
Why would it need to be pointed out when there are already cross-references that a reader can use to reach a conclusion that's already rooted in the power system?
Gojo says the reason he took less damage than Sukuna from UHP is because it consisted of his own CE. Therefore, if we were to apply the same logic to Yuji, he would take less damage than Sukuna as well—given the multiple statements confirming that his cursed energy is, quite literally, the same as Sukuna's.
I also wouldn’t call such an early concept random, considering Yuji’s natural resistance towards Sukuna was established early on in the series.