Totally understood, and thank you for your effort + time to reply to this topic! I didn't imagine such a basic behavior of feeds would be "downgraded" with this migration, but here we are. It's sad, but as you said, we can't expect much from a side project anymore.
Quick question: if I were to migrate back my subscribers to my main/native WordPress feed, there wouldn't be anyway to redirect all my FeedBurner feed's subscribers back to the original one, right? Only the other way around…