If the verts are not exactly at the same distance to the plane you want to cut then you will want to be mindful of the viewport orientation before using the knife project. Since my verts were at the same depth as the plane I was cutting (and both were perfectly flat) then it did not matter.
If my verts were hovering above the plane then I would want my view to be a left orthographic for the Knife Project so that it projected directly to the side (hopefully that makes sense). It is similar to UV unwrapping when projecting from view. IF your view is in perspective then your cut will be skewed off to the side when you probably didn’t want that.
