+1 here, got the email for one of my accounts to. Sounds like they just cut off a big part of their ad revenue. Maybe this has been the plan all along, keep affiliates until their advertiser portfolio was a bit more balanced. I don't think it's affiliates in particular that they're after, just the poor quality offers and/or false promises that most of us use to push our offers.
Then again.. maybe it's really someone gaming the system. If they did it right, FB wouldn't be able to tell and may just continue their warpath on the falsely accused ads.
It could be both. I received a notice on an account I haven't ran ads on for months, which is saying that these emails are getting sent out based on past data. It's definitely possible that if a bot(s) was/is running, it could have been running for months, and then it could have impacted that past data.
The decision to send the email is probably not an anti-affiliate move; performance advertising stands to grow on FB and constitutes a majority of ad spend as is. It's definitely a move to get rid of misleading ads.