The thing you plug into your computer is STILL not an antenna.
You don't have to plug anything into your computer. They are describing the size of the antenna by comparing it's size to something you are probably familiar with, a thumb drive. Read it again:
Except this next generation antenna is no larger than a thumb drive that plugs conveniently into a tablet, smartphone or desktop computer.
It'd be like me saying, this widget is no larger than a breadbox that sits on your kitchen counter. I wouldn't be saying the widget was a breadbox, nor that it had to sit on your kitchen counter; I'm only comparing the widget's size to something who's size you should be familiar with.