jay didn't participate because 9/11 happened after jay premiered Takeover that same year on summer jam...just put 2 and 2 together....you can't get both of them together during this time at all
jay did some freestyle about giving back to 9/11 victims separately, but the blueprint dropped the same day as 9/11, so he namedropped his album with 9/11 and said some of his album proceeds went to charity
having one side of the answers from nas point of view is not enough to get the full picture...just see the full scope of things of how things were
also there's old videos of nas talking about 9/11 and there is supposedly an unreleased track of nas rapping about 9/11 just to make sense of it all