Actually, FAF (First Active Frame) is and is not the same as an IASA (Interruptible As Soon As) frame. Ganondorf's IASA Frames start immediately after the hitbox on Frame 23, which is the peak of the kick itself and the end of the hitboxes. Anything after that can be interrupted into another attack (like F-Tilt). If you notice, there is no data in the listing that lists out the FULL frames of any of Ganondorf's attacks, and as such, one can assume that FAF means his full frames of his attacks, not his IASA frames.
If you still do not believe me, try using Ganondorf's U-Smash and then interrupt it at the peak of the hit, which is frame 23. The IASA frames start at frame 23, which is the last active hit of the hitboxes. It doesn't take almost a second to interrupt Ganondorf's U-Smash, whatsoever. 3 consecutive U-Smashes can be used within around a second if you IASA the last hitbox frame comes out.
So there is an attack of Ganondorf's that is fast comparable to other heavyweights, and it's also the reason Ganondorf's the only heavyweight able to combo into two U-Smashes. Because Bowser, D3, Samus, Charizard, Falcon, DK, Bowser Jr., Link and Yoshi do not have the same IASA frame advantage Ganondorf has, they sometimes will be unable to link into a second U-Smash in a true combo; although, they can link into U-Smashes if they can read opponents, but not in true combos most of the time. Somehow those characters cannot interrupt their U-Smashes very early, and often have to wait for their animations to finish, but Ganondorf on the other hand can literally do it AFTER the peak of his attack.
So in conclusion, Ganondorf's IASA is 23, not 42. (Go test it out yourself if you don't believe me)