You're not addressing GP's point though. If all of the managers were chosen for their technical expertise then it's likely that their employees won't highlight technical expertise as an important feature of their manager because they don't have any managers who DON'T have said expertise. They probably don't know what it's like having non-tech managers.
E.g. i'm sure few employees would say that they really appreciate that the air they breathe at work has adequate oxygen in it. Does that mean you should then cut that in half because it's not important ?
Back to TFA there's this sentence: " What employees valued most were even-keeled bosses who made time for one-on-one meetings, who helped people puzzle through problems by asking questions..." Well, let me tell you... i've worked with some pretty darned smart / good finance people and CEOs and Product Managers. Very few of them (ok. none of them) could ask relevant questions about technical problems to help me work through technical issues. Why ? because they didn't know anything about the subject. Heck they didn't even understand some of the nouns in what i was saying. Go ahead... go ask your finance guys about how you're trying to figure out why the cache hit rate in your application is 20% lower than you expected or something. About 30 minutes in you'll be 5 steps away from your original point and explaining how the internet is like a series of tubes! (which btw, i actually think is a reasonable first order approximation ).
One problem in TFA is that it looks at "deep technical expertise" as meaning having greater depth and breadth than all the people working for you. That's going to be pretty hard. You may start out that way, but as you get more people, if it's still true then either you're Donald Knuth, or you're not hiring A players OR you're working at a large company where your group has a very narrow focus. e.g. if you're the manager of the Oracle optimization group then yeah, you can be the best at that. If you're the Dir. of Engineering at a small company it's a heck of a lot less likely that you can be "the best" Photoshop guy, DHTML guy, Java guy, Ruby guy, DB guy, sys admin guy, network guy and architect guy all in one. If you are... especially after a year or two in your role then your people are just not good enough. There should be no way you could keep up with 7 guys focused on only 1 or 2 disciplines each when your own main focus is management anyway.
With people who have worked for me and with my peers i could "dominate" the jr guys but with the Principal engineer types I had enough base knowledge and experience to be able to ask intelligent questions and come up to speed quickly enough on the things my guys were struggling with. But the only reason i CAN ask good questions is because i have actually do have strong core knowledge in dev and admin and also, due to experience or nature or whatever, i'm pretty darned good at debugging code and systems. If i didn't have that all i could offer is stuff like "do you best" and "huh, do you need more resources on this project?" and things like that.