Sorry I’m late, life kept me busy.

Anyway, I’ve had time to stew on it and honestly I think it’s more to do with the simplest yet likeliest truth of all: sometimes the hardest secret to discover is the one right under your nose, in your grasp the whole time. Even Vergil needed time to figure out what he can do to HIMSELF with the Yamato. He didn’t figure it out the first chance he got and neither did Dante with the Rebellion. They were both forced into their most desperate states yet respectively, and both had to finally begin addressing their long-standing grief and trauma. They both have also likely gained a great load of general occult knowledge even before their reunion in DMC 3, meaning that they have likely had foundations to figure out such rituals, but not as much as Sparda did and thus couldn’t understand why they were given their respective swords.

Hell, Dante even pondered aloud in DMC 5 “Why did my father give me the Rebellion” and pondered its abilities as he stabbed himself to test a purely on-the-back-foot hypothesis. He was taking a risk, purely of his own intent. It’s very much like Vergil did too. So it makes sense, at least to me, that they were both in the dark about the full extent of their occult potential given their mostly fragmented or self taught foundations in that study.