I've never been a product manager but IMO it probably goes something like this:
"The framistan line is successful but I hear from our customers that we should have some options that add [x] and drop [y], while having support for more [z]."
"We need to create a new line, a totally separate brand from framistan that has way more [x], [y] but no [z] at all. The competition has entered this space and there is clearly a market there."
They say this as often as they can, iterating over various x, y, z triples and they maximize the product line, perhaps until they hear feedback like yours.
Apple, OTOH, does whatever they want, targeting limited segments in order to keep everything simple. They lose out on lots of opportunity by restricting themselves to just parts of the market. But they also have a money tree, so it doesn't really matter.
Re: nonsense model names. As a technical consumer I much prefer these very-distinct names that change with each new release. When I read a review, it's very likely that I'm reading the right review. When I'm buying used, it's very likely that I'm getting the right product. Brands like Amazon Kindle Fire, MacBook, IMO make searching for and finding the right stuff harder. I can appreciate the elegance of a simple product name, though. Typically they're concealing the true model info under some other header, but it's usually harder to identify.