That's kinda strange as I don't think it can guard Takuma's f~b~f+P.
I think it just means that Takuma's Zanretsuken is more of a "throw" than an "locking attack" or "attack throw". Also probably has to do with the number of blows, how much stun there is in between each blow, and if all hits of the blow can pull you into an animation.
There seems to be a large variety of hit-types in KoF; moves seem created on a "move to move" basis, to some degree. Makes it very interesting to learn what one can, and can't guard-point.
Oh, and general rule of thumb, guard points only pertain to the area that's actively casting the guard. Like with Terry's back in Rising Tackle in 97, Maxima crossing his arms over his body before his crouching C, or Kyo turning his back/shoulders to you before his DP in various games, there is normally an animation of some guarded body part or something being displayed, before the move gets to the "attack" portion.
These consistently apply to the upper body, and never the lower (if they DO do block low, it's probably a counter or parry, not a Guardpoint), with very few exceptions. Maxima cheats it a bit now, with his "Full body shield!" that he gets on his DM & EX DP+k, and Takuma had that full-body defensive stance in the 2000-series, but that's about it.