Note the company he's in...
The reader is the manager of a *small* IT department, where it is not uncommon for people to have to wear "many hats". I manage a small (two person) IT organization myself, and while I don't *have to* know how to program, it's certainly been handy, and it's allowed my employer to use me to write internal systems that we'd either do without or have to bring in an expensive consultant to do. Furthermore, having someone in the role who understands both sides of the fence makes it much easier to get things done, especially troubleshooting.
I also agree with apotheon's sentiments, in that being able to understand the work allows you to better work with your employees. What kind of manager are you if most of what your people say flies over your head? It's up to the IT manager to translate the tech to the business, not the tech folks to explain the tech to the IT manager...
J.Ja