Envelope points that fall directly under a column or a pedestal are not designed.

Question

I found this statement " Envelope points that fall directly under a column or a pedestal are not designed." in another forum in here and it was made by a moderator, I believe. I cannot find any other information as to WHY it will not design the reinforcement under a pedestal. I am designing a mat foundation with pedestals and piles underneath. 
 
 The other discussion, for reference: Slab Designer in Staad Foundation Advanced - RAM | STAAD Forum - RAM | STAAD | ADINA - Bentley Communities 
 Can someone please explain what is going on with this? 
 Thank you!

Kris Sathia · Answer

There is a pedestal design facility in the program for designing locations where a pedestal is present under the column. The principles of column design are used to design the pedestal for axial force plus biaxial bending. There is no specific instruction required from you in the sense that they get designed when you ask the program to design the slab. The calculation report should contain a segment on the output for each pedestal that is designed. 
 If there is no pedestal present, and the location (on the mat) being designed happens to fall within the boundary of a column, the design is not performed because there is no clearly defined effective depth. In theory, the depth at that location is the mat thickness plus the column height, but it is not clear what the accepted practice is in design offices for designing such locations. Hence in SFA, those locations are not designed. We think most users have agreed with this decision.