Well, if it's all a taste issue, then I'm more with the +14k first buyers of "Sisters" than the 35k first buyers of "Scandal Nanka Buttobase", by a lot of reasons we all have discussed here before.
Furthermore, @spacecadet, I do really know that the regular fanbase expect a single released few weeks before the upcoming album, and if you read my reply with some attention, you'll find out that I said almost the same as you; so, there's no surprise. I was talking about single releases, I was making a comparison between singles only, and not between albums and singles; if I may say, this actually is a completely different situation. I can definitely buy an album after a single I didn't buy because it'll be on the forthcoming album's tracklist, but I'll think twice if it's a single that is being released shortly after the previous one, because 1) I may not have money enough to buy it yet, and/or 2) I'm not sure if I would patiently wait for the next album release to have this song in my collection, since the next album hasn't been announced yet.
But meh, there's a very important detail: I actually love this single. Both songs are great and help me a lot while I'm trying to focus on my personal goals. And I can easily say that, if we are comparing these two singles before mentioned, I prefer "Sisters" a lot more. It sounds as mature as they're now. I barely listen to "Scandal Nanka Buttobase", it's one of my least favourite singles of them. But the impressive first week sales of it could have been a reverberation of the "TEMPTATION BOX" successful promotion. The girls were on the hype at that time, if I remember well. To me, it's the only way possible I can understand these high sales of SNB (and the fact that four different versions of it were released - in their whole discography so far, it was the first time it happened and only happened again with "Yoake no Ryuuseigun", four years later; and in the specific case of SNB, three of its four editions were limited ones), because the song itself sounds bland and incredibly superficial to me. I can't feel the girls: they aren't "there" on it.
You guys may say I have a bad musical taste, and I may completely agree with you. But there's nothing we can do about it, right? Musically and artistically, SCANDAL is becoming a multifaced trademark now; cases like this one will happen with more frequency. The fanbase is getting bigger (I think, at least; because of the world tour and etc) and more diverse/heterogeneous, and this can be interesting (less previous music tastes among the same fanbase or different points of view converging to the same common interest). We can share opposite thoughts in a good and constructive way, like I hope we're doing now.