Agree about c/w thingy, it's just the B-Sides!
If I could give an example, maybe normal singles is just like
Utada Hikaru - Be My Last?
The single has just only 2 tracks, the song itself and instrumental~
Anyway, If I could see another artists release like
Otsuka Ai & YUI singles, they always have a normal A-Side & B-Side and additional songs sometimes, maybe they release are just an example of
Maxi Single. 