Clannad has too many choices to my taste, but what you point out is something I really love in this VN : I love when routes aren't just the given heroin's stronghold with nobody else existing anymore... in fact, for me that's probably the weakest point of VN in general in comparison to other story telling medias (having a route system gives the scenarists an excuse to do so, simplifying their role...).
Most of the time, you just get something approaching when the scenario needs it (love triangle and such things).
Of course, I'm not saying "give a chance to heroin B while being in heroin A route", but thinner walls is a good thing to me.