And you didn't read the answer, it's literally stated that MS does not cover that area -> UV wasn't negated there.
It's stated that's the effects of UV are weaker on curses which might refer to Mahoraga or Sukuna in that context, but more probably Mahoraga, which also doesn't mean anything because stronger effect doesn't mean you can't think, as its shown in Sukuna's case, Gojo didn't question how Sukuna summoned Mahoraga btw, so it's not an issue in the manga as its also stated that Jujutsu mastery is based on how you can ignore hand signs or incantations when you activate a CT.
Again, MS sure hit didn't overlap with UV with regard to Megumi's area, that's blatantly stated in the same chapter, it's stated that Megumi was vulnerable because UV was active on him directly not that the damage was transferred to him, while you're assuming that Sukuna transfered the damage to him manually.
Mahoraga destroyed the domain in 0.01s, not the time Sukuna was hit fully is 0.01, when Mahoraga was summoned, he immediately destroyed the domain in 0.01
Everyone was watching the fight and when Sukuna was caught in less than 0.01s even Yuta could perceive that, and even Gojo said the difference was less than 0.01 but it landed on you, which really implies this was the first time it landed, if it landed before then Gojo would've noticed this.
And again even if we assumed UV targeted Sukuna but he transferred the damage to Megumi (which isn't implied anywhere as the narrator directly states it wasn't cancelled with regard to Megumi, so UV directly attacked Megumi) it wouldn't mean Sukuna took some damage.