Actually, the Facebook will only ban the ICO advertisement when it is indicated as the scam ICO. Or, it may be indicated as scam or spamming advertisement pf the ICO. However, regarding to the continuing ICO after banned by the Facebook, I also don't have any idea about it.
yes, maybe this is the facebook reason why they ban the ico, but we still don't know what exactly their reason. but I don't think that Facebook will continue to do this because I see that the facebook can get another profit from the ads so maybe in someday, Facebook will allow the ico ads to be shown in the people's page. or maybe facebook wants to use the ads for their coins promotion, and they want to reach many audiences to learn about their ico. but lets we wait and see what will Facebook do in the future.