To us, attention to detail matters in its application. Intricate machining that contributes nothing to functionality is window dressing (that only has the appearance of doing something but is superficial and misleading). Function over form, and form follows function, are honest and unambiguous.
Today we look at the relief on the URF, specifically, the section before the 1913 rails start. A simple 45 degree relief on both sides allows a flip up BUIS's sight stalk to be more quickly and easily accessed. Simple solution to a simple ergonomic problem. Nothing more is needed, so nothing more is done.