His theory might be true if you were only talking about writing a program from scratch. But programming is a lot more than that, because except for the smallest, most trivial exercises, programming is a team sport. Which means you need to be able to understand somebody else's code, and you also need to be able to modify it in a way that makes sense.
You can have a program which is beautifully structured, and factored in an extremely clean way. But what happens when you have to modify it in response to a change in requirements? And what if you have external code that depends on the existing interfaces? At that point, the skills needed to be a good programmer are quite different from that of a writer.
I can think of a number of novels where it's obvious some scenes got moved around for plot reasons, and their were continuity errors or other ways in which the seams showed.
But novelists only have to deal with that for maybe a year or so; programmers have to deal with this problem for potentially decades, and at that point it's a completely different problem just because the scale is different.
I'm working my way through Stephen Donaldson's latest Thomas Convenant novel (book 9), a series he started writing in the 70's (first book published in '77). He expects to have the final book (book 10) completed by Fall 2013
You can have a program which is beautifully structured, and factored in an extremely clean way. But what happens when you have to modify it in response to a change in requirements? And what if you have external code that depends on the existing interfaces? At that point, the skills needed to be a good programmer are quite different from that of a writer.