Yes, I don't want apps accessing my messages surreptitiously. Points there.
However, what's wrong with allowing another app to post messages to my messages?
If I don't want it, let me turn them off. Maybe, as a UI expert company, it's easy "block app from sending me messages" when I get a message. Seems like something that should be fairly transparent to the (potentially misbehaving) app.
I use a Garmin, and Android, and I use it for messages all the time, it's great. I can't imagine not taking them. It's easy for me to block stuff I don't want, could it be easier, maybe...
But my point is this isn't something unreasonable for a user to want.
As a general aside, it seems when I hear about Apple products anymore, they are locked down, unintuitive, and generally just unpleasant. I even tried an Apple device again recently...eugh.
Apple is only "nice" for a certain, narrow segment of the population.