[ImpactBreaker]

Well whether it matters or not the japanese music companies, such as avex, constantly use the term "a-side" to refer to certain singles they release such as hitomi's kimi no tonari which was considered her first TRIPLE A-SIDE single.
The term b-side came from old vynils which had the main songs of the album on the a-side, and miscelaneous stuff such as bonus tracks and interviews on the b-side. While i agree arguing around whether something is an "a" or "b" is purely relative and clearly never gets to a point, certain songs are clearly a b-side and it's pretty much hard to prove otherwise: Shiina's ringo Jitsuroku -Shinjuku ni te- Marunouchi SADISUTIKU~ Kabukicho no Jyoou [Documentary -In Shinjuku- Marunouchi Sadistic~ Queen of Kabukicho] is clearly a b-side.