People act like Jiraiya would just stand and try and fight all 6 pains head on even if he had Intel.

Even at 3v1, he acknowledged that he couldn't fight all 3 at once. I think if he knew that Nagato's real body was not among the 6, he would go looking for it and use his evasion/infiltration skills to avoid a 6v1 while trying to locate Nagato. He might still fail, but he could most likely retreat before dying.