In the context of the article, it's an end-user feature. Just as having the ability to use anything from a 10" netbook screen to a 6-monitor array is a major feature of PCs that could not be equaled if there were only one or two PC models on the market. Though surely it would be cheaper and easier to develop PC apps if there were only one or two models.

Considering I'm typing this on my phone's physical keyboard, I'm a big fan of the fact that hardware diversity allows me to find a phone that fits the way I want to work.