He assumes that the design of dwellings should be determined by the aesthetic quality of their exterior front view. But the owners spend the most time in the interior, and second most in the back yard.
If you want to make the best use of the interior space, you don't carve up a half dozen secondary masses (using the article's term). You do this because you have bad taste and think it looks fancy/expensive. i.e. You think it looks like a proper mansion when in reality your 3000 sqft house should not be carved up into half a dozen independent chunks as if it's a palace built up over 4 centuries.
Maxing out the use of the interior space means one huge box, which is what most "ultramodern" houses in cities are. It's not my aesthetic, but it least it makes sense, unlike putting tacky form over function in the mcmansion style.
I too wish he'd written about more than the façade, but this piece is only the first in a series. He goes on to talk about garages and columns, so perhaps he'll get to interiors.
