I'm sure they're referring to upgradability which is the last attractive feature of desktops. I can't figure out why anyone would care how big their tower is. If you're going to have an array of 6 monitors, I'm sure you've got an extra square foot or 2 for a standard tower that won't lock you into HP components.

You'd be surprised how much two square feet cost in a trading floor in Manhattan. Plus enterprise customers are typically "locked in" anyway.