If that is what the author is trying to say, then I think they are stating the blindingly obvious. Hire people who understand the fundamentals - that goes for every single job and is a given.

"There is nothing special about the web that makes it more or less challenging than designing on an iPad. They are just different."

Differences are exactly what makes something special. Specialists are those people who have in-depth knowledge of the differences and know how to make use of them ... and know how to make use of those differences now, not after they experiment and figure things out from first principles.

So advertising for an OSX designer, or an Android designer is a sound decision. I've run a team of Solaris sysadmins and yes I could have hired Linux sysadmins (unix is unix as the cliche goes) ... but I won't - Linux admins may know the fundamentals of unix, but I want people who really understand Solaris and how to get the most out of it. And I don't want to wait whilst a Linux sysadmin learns the differences between them.

To be a little critical of the author, it doesn't sound like he has much experience as a designer - the blog post sounds like something written by someone who doesn't know what he doesn't know. Isn't the saying that the 'devil is in the details' (or differences) ... I would have thought that a good designer would understand that and never argue that all you need is generalist knowledge.