No one knew that Japanese torpedoes would function in Pearl Harbor, which was believed too shallow to defend against the threat.
The extent of the success of the Japanese attack need not have been predicted for the “Roosevelt knew” hypothesis to be entertained, only the likelihood that Roosevelt may have wished for the Japanese clearly to strike first.
So, if he "knew" then he could have gone to Congress with evidence of a Japanese attack, but didn't do so. Do you really think that makes sense?
Tell you what...Go ahead and post here any actual evidence you have that FDR knew in advance that the Japanese planned to attack Pearl Harbor. Let's see it.