Jobs was principled yes, but very smart people, while principled, aren’t afraid to change their mind when they discover new information. Case in point, the iPhone 5 was the last iPhone Jobs was involved with, and the first to have a bigger screen. Hence, he was already beginning to change his mind about something he had been outspoken about. I have no doubt that Jobs would have eventually come around to the benefit of the even bigger displays we see now when he saw how they could benefit the customer.
Being willing to change your mind is a key part of the creative (and product development) process. Jobs knew that. If it turns out there’s a new product category or need for a new product line with combined macOS tablet / notebook, Greg Joswiak and has already stated they see them as two separate products, yes, but that they can’t rule out changing their minds.