It's a bit surprising that there was no(?) target sight for the Patt.14 that did not require drilling across the rear sight protectors, considering that the backsight axis screw is not that far away and its hole already goes through the left side of the sight protector.

Without getting one out to look, I presume it was a problem of clearing the sight ears while keeping the sight body close enough to the bore axis that there was enough travel on the windage bar.