There seems to be too many gaps in the data to firmly draw that conclusion. I mean, I don't think shifts are effective except against extreme pull hitters, and even then they keep using the shift on pull hitters despite the fact that they are able to effectively change their approach. Partial shifts don't seem to be effective in general, and full shifts are only effective against players who refuse to/cant effectively change their approach; walks don't have anything to do with that. But I wouldn't be surprised if the type of hitters which get shifted on already walk more than the rest of the league, regardless of the shift employed. So I agree with their conclusion on when to use the shift, but not necessarily for the same reasons, I don't think we've been tracking the right data to draw any conclusion about shifts and walks, or at least not enough to say its a primary reason not to use them.

And seeing as how most the players who get shifted on are power hitters, I wonder how it affects them psychologically, as in, do HR's go down when you are employing a full shift?