Intersect Faces results in new hidden edges

This doesn’t happen all the time but it’s confusing when it does. Bisecting this solid using Intersect Faces With Selection results in many hidden edges being created on various faces. It doesn’t occur when intersecting faces with Context or Model (though I have experienced it at other times on other models). Thoughts?

2nd Fl Walls_ Ext.skp (920.7 KB)