Actually, the article's title is "Six
of the Best Real Instrument Emulations". The critical weasel-word there is "
of", implying that these are just six good ones, not necessarily THE best.
At least, that's the only way I can imagine them justifying the list they came up with.
One of them isn't even an instrument, by my definition. It's a loop library. Another is an emulation of an emulation. None are string libraries (sorry, VSL, you're just a wannabe) or guitars. None of the top-tier virtual instrument brands are even mentioned.
The only way this list makes any sense at all is that they meant the title literally,and this is just a random sampling of some good instruments.