First of all, take in mind that the author of the above statement is talking about website development. So he is worried about presentation development, and that's where he thinks Scala would not be a good choice...
Having said that, I do have a good experience with web development. I've worked for at least 8 years exclusively with it, 5 of that in digital agencies.
That's, in fact, one of the main benefits of using a specialized and interpreted template language like Velocity. It's easy of use, power and flexibility are adequate to presentation-layer developers. And then server-side guys are free to use a serious, statically typed language everywhere else...
However, I also agree that Scala is somewhat different. Being at the same time much less verbose and much more expressive than Java, I believe it could be used for presentation development - so maybe it could be successfully used as a template language. And if it also could be combined to a framework like Play (which compiles the web site automagically after every change), it could be a winner IMHO. Still, even Play has opted for a Groovy-like (dynamic) template language, which is not a good sign.
To sum up: the problem with Scala is much more related to the fact that it is compiled. In fact its type inference mechanism makes you almost forget it is also statically typed.
(And sorry about my English. Let me know if something is not clear, I'll try to fix it up.)