I suspect that part of the answer has to do with the face of the clock, and the fact that Fluther moderators are primarily – but probably not always – based in North America and primarily available during daylight and evening hours there.
When Indian spammers might be… um… “working” at producing that junk during their daylight hours, it’s after midnight in North America, and even early risers on the East Coast don’t usually start their day before 7 AM Eastern Time, which is the end of a work day in India. So spam produced during daylight hours in India and posted to Fluther at a convenient time for the spammer has hours to sit there (and collect flags) until a Fluther moderator can see it and deal with it.
I don’t know how frequently Fluther gets spammed by North American spammers (and it could be just that they have better-automated spam production, because if you think about it, creating an account on Fluther and then posting spam is a labor-intensive task, especially to reach so few eyeballs, so maybe they just plain “don’t do it” here), but spam that hits here during daylight hours when moderators are at least “available” to take care of it, can be dealt with more quickly.