I don't think the argument is about (or entirely about) attractiveness (or lack thereof) of high margin sectors. It's about being able to thrive in that kind of environment.
For example, Apple cannot thrive in the same kind of environment as Dell. Apple's corporate culture, habits & history would put it at a disadvantage in a world where margins are thin because it has not evolved or been optimised for that environment. In a world where competitively driving down costs via stock turnaround times & cheap production determine success Dell has the upper hand.
Similarly, in a world where revenue per employee is low, a company such as Google might be ill equipped.
I am not agreeing or disagreeing with this position (I don't really know enough to). I'm sure you could argue other forces at play might be more significant or that his assumptions about Google's tactics are incorrect. But it's not nonsensical.
What I did find unclear was which category he places himself in: SMB software or enterprise. But that's a limitation of the medium (personal blogs). Some background is assumed. I'm willing to take that as it means writers don't have to start from scratch.