No, Apple should have no duty to explain itself or demonstrate what they say is true.It could be a win win if Apple simply showed how bad it would be on the A12X/Z iPad Pros. If Apple were actually honest to begin with, being transparent about it can push more people to upgrade.
Either you trust Apple or you don't. If you don't trust them and even think they're lying or misleading you, why are you a customer? I would never be a customer of a company I don't trust unless I have no choice.
Apple's domain is to create their products and services. Customers should have no say in how they do this at all. There should be a Chinese wall between the development and customers.
Customer's domain is to buy the products. Or not. Apple should not interfere here. I would be completely against any law or regulation which gave Apple the power to force customers to buy their products.