Given the fact that the grips on original production guns are fitted while the piece is still 'in the white' that would indicate that those grips have been fitted flush - thanks to the sanding and buffing.
Many times - photo angles don't give the 'actual' view of 'all' of the piece and in this case you may be seeing the leading edge of the straps as reflected by ambient light.
Most likely, though - you're looking at guns with replaced grips...
Scouts Out!