That problem is just with an Apple user to an ex-Apple user. In other words it's a problem that Apple exclusively created and they benefit from not fixing it. It just means a current Apple user goes to text you and Apple thinks you are still using imessage so instead of sending an SMS message it sends it via their imessage service. Apple likely makes this process a pain to make it harder for people to switch OS'es and makes you more locked in. Not only are you going to lose your imessage groups, but you'll also have difficulty for awhile with getting messages properly.
