It seems that because the window is only cutting through part of the sweep at the sill that the sweep will not fully cut. But that does not explain why the window head projection is cutting when the window is not passing through the sweep.
Meh, I am just going to lower the window 1/4" and cover the detail in 2d.
Sad detail really, why anyone would lower a window through a brick sill is beyond me. This is not my design btw.