Jin said it wasn't a priority but that didn't stop J from telling them all anyway. This is not what happened. The missing part of Jin's data is not J, the missing part of Jin's data was absorbed into Messiah with Hiromu's parents and Youko's mom and the rest of them. This isn't speculation, this is laid out in the plot of episode 40.Darkwings wrote:Since he created J, if he used his own data to create J of course he wouldn't want to retrieve it now: he needs J to fight.
Also they wouldn't have set up this rivalry between Enter and Hiromu just to have J deus ex buddyroid the final battle. To me, that is not good storytelling, at all.