Where is it used like that? I don't see drawing_state.transform.m11 used anywhere by itself.
I don't think the reference was terribly clear, but d2d_transformed_geometry_StrokeContainsPoint() does this as well, introduced by commit b88f06fd3425e04ed6148ba88d0a9dc40b654fcc. It's clearly not ideal, but it does help the common trivial cases.