This was my thought as well. He was in Roger's crew after all. It would make sense that he would know everything leading up to the actual trip to Laugh Tale (since Shanks stayed behind), and that Roger would have probably told him what happened when they arrived there. How they made it to the finish line, but didn't have the right pieces in play to be declared the winners, so they just laughed at their wasted efforts. He probably told him to keep an eye out for when the missing pieces show themselves.
I'm actually curious if he knew the significance of the Gomu Gomu no mi before he actually stole it. I'm sure he probably thought it was a powerful fruit before he took it (hence the high security), but not the fruit that Roger was missing during that fateful trip. Maybe that's why he went to meet with the Gorosei a while back. To confirm his suspicions about everything going on.
And to discuss what someone posted earlier, just because the name of his devil fruit changed, it doesn't mean that all of a sudden he's OP. We always knew he was gonna awaken his devil fruit sooner or later, and that he would be able to turn things into rubber like how others who have awakened can manipulate the space around them. I just feel like his awakening coinciding with the massive lore reveal might be clouding people's judgment about his abilities. He's still gonna be rubber boy with all his Gomu Gomu abilities, but now he's gonna be more significant to the overall lore of the story beyond just finding the One Piece.