I feel like it has to be financially motivated and the only thing I can think of is they want users paying for premium directly rather than having it gifted from a different accounting bucket. But that doesn’t seem like strong enough motivation on the surface.
From the post: TL;DR With the API changes now in place, we no longer believe we can effectively perform our mission so we are sunsetting BotDefense. We recommend keeping BotDefense on as a moderator through October 3rd so any unbans can be processed.