Allen, My opinion that. Note C is a fillet weld shape. General welding sequence. Flange joint should be weld first before welding on web to flange corner end. This is just my own idea. I also still confusing why code have to mention that!
I think the idea is to cut that access hole in the web before putting the flanges on(built up shape made out of plate)....and idea of not wrapping the end with weld may have to do with the possibilty of creating a notch in the web when welding around that end.