A cotter pin, while being round also has two openings that act just like the blade on a block plane; Lots of wear. Further, I don;t think you are capturing all of the design intent here. They are securing the clevis so that it only rotates inside the steel part. Steel on steel should not have a major wear issue, but that is not the case with steel rotating on alum, which is what happens if the pin is not captured to the Alum part. I suspect this won't see a lot of use, beyond vibration, but pretty sure that is why they are using safety wire that way instead of a cotter pin.
Also agree with others that a cotter is just too soft for this application. Their only job is to keep a nut from loosening or a clevis pin from sliding out and they have a design goal of being easy to bend, which makes them inherently weak. They are not structural in any way shape or form. Take your 1/8 cotter pin and bend it (can probably do it with just your fingers) then try to bend the 1/8" clevis pin or a #6 screw (a little under 1/8" at it's minor diameter). HUGE difference.
Lots of folks reacting probably not because this is a major issue with a baggage door latch, but if you start to follow this approach to more critical areas, you end up with a poorly executed build. Substitutions like this can lead to major problems if the engineering is not fully understood. Not saying that I fully understand it, but do understand that deviations can create compromises.
Larry