This is a reasonably common technique in game engines, actually, usually referred to as an “uber shader”. The idea is to have one massive shader with a bunch of

This is a reasonably common technique in game engines, actually, usually referred to as an “uber shader”. The idea is to have one massive shader with a bunch of if’s that does everything, and then you don’t have to pay the cost of shader state changes. There are lots of arguments for/against the uber shader technique, but I’m guessing it was probably intentional for performance reasons, not just an accident of development.