Are phones getting bigger on average, or are we starting to notice the bigger phones because there are more smartphones out there (thus more large smart phones)? Does this perception exist because it is easier to notice bigger phones, since small phones are less noticeable and easily confused with feature phones? People also tend to talk about the models with higher specifications. Those impressed by gargantuan screen sizes will clearly bias perceptions, but even a faster processor creates an upwards pressure on size so people talking about those models will bias perceptions.
I bring this up for a couple of reasons: the article was more concerned about model releases and, periodically, the number sold of a particular model. These are not overall market statistics, so they are meaningless. The second reason is that there are plenty of smaller smartphones on the market, some of which are smaller than the original iPhone. That seems to indicate that there exists a not-so-often discussed demand for smaller phones. Perhaps the demand is high enough that they dominate the market.