That’s exactly the reason for the slowdown though. Phone shutting off = new battery under warranty. Phone silently slowed down = increase in new iPhone sales.
I’ve been on the fence about this whole battery gate deal. After all, I own some AAPL shares. But what you just said kind of hits the point. Having dealt with Apple’s support over various times in the past, every single encounter I’m crossing my fingers they would continue their generous ways and cover the issue — which they should. But by engineering an intentionally vague symptom of a real underlying problem, it gives their support staff some leeway to interpret each case and whether the customer gets the coverage (eg. Do they buy a lot of Apple products or have AppleCare on a lot of existing products owned?)