I've never understood Twitter's "anti-spam" effort. The only "spam" I've ever seen on twitter is when someone I am following likes another tweet, or it tells me I should follow someone because someone I'm following follows them. I'm not interested in either of those suggestions. I'm only interested in what the exact account I'm following tweets or retweets, because I decided to follow it.
It seems to me that if the system worked as intended, I would see none of this mess because I'm not interested in following the bots. They can tweet away all they want, hundreds of thousand of them, to crickets.
I would venture to say that the "spam" is less of a problem for what users really want and more of a problem for their efforts that try to increase user retention/engagement and therefore ad rev.