A lot of times, you can tell he's vague so people don't guess shit.
Even with this Gorosei information. He's making it seem like they knew the whole time, but 2 chapters ago they mention that it was a rumor they were told basically, as if someone told them the rumor.
I.e. they knew the fruit was important, but not why until recently, since they weren't concerned about it literally until 1037.