I think it's because MAFC has roots in NCL which has roots in APT, but I have found that during computation, Catia only considers the tool up to the cutting length of the tool- even if you specify say a 1" contact point on a tool with only .500 flute.  This is important when trying to use a relieved shank endmill.  I have had paths that WOULD not come out- gouged walls, very difficult- even with guiding boundaries...until I made the flute length much longer...then the path came out correctly.  We have to remember that the point is to make good aptsource.  Even if the tool is defined incorrectly in Catia- we can always easily change the note on the tool-list or set-up sheet to reflect what we "really" want.

I can't think of a good fix for this other than to automatically for computation purposes consider that the tool is fluted for the entire length?

Maybe some of you can think of a better idea.

This rarely becomes a problem- usually only with walls that are tipped into eachother at extreme angles where there is a lot of fanning.  Most of the time, it is okay to define the tool exactly as we want it.