I see what your question is. I agree, Roger doesn't really show what he does on ends, although you can see from the first pictures in his article, which is to just sew the front and back together.
I am a novice, but when I did it, the baffles go all the way to the end so they just sort of wrinkle up there and there's actually a gap that the down could theoretically flow between baffles, but in actuality, it doesn't.
I've been experimenting with just doing sewn through baffle, but having the inside fabric spacing an extra 1.5 x the baffle width (actually pi / 2):
Then, at the end, have the liner fabric and extra 0.75 x baffle width longer:
Just fold it over to consume the extra 0.75 x baffle width. Maybe you can see from thos pictures.
Maybe you could do the same thing with conventional baffles to have the loft go all the way to the end.