They should give you SOME kind of reward to absolute completion!
I agree with you: the B-sides are too much! I feel like I'm in a Super Mario Maker tournament every time I even attempt. It's fun to try though! Sometimes.
The joy of completion doesn't count? ;)
I don't mind the steep difficulty. They're just waaaay too long for how hard they are. B-side Summit is like 40 screens.