It's a bit like saying "don't they know human flight existed before the Wright Bros." or "don't they know cars predate the Model T?"
Of course, but the iPhone (and subsequently Android) presented a gigantic turning point in mobile development, to such a degree that mobile development can largely be categorized into "pre-iPhone" and "post-iPhone".
Pre-iPhone mobile development was a vanishing small industry compared to today and used technologies that are largely completely not around today (see: J2ME, Symbian, Windows CE).
So yeah, maybe they could've said "mobile development in the modern context centered around multitouch-centric interfaces using soft keyboards has only been around 8 years", but that's kind of a mouthful, and unless we're trying to write an accurate history of mobile software, not particularly relevant to anything.