I was a developer at digg from 2007-2010, and I can say his statement is just flat out wrong. Digg did hire great PHP programmers, but that was because they were great programmers, overall. Every single one of them moved, with ease, to other languages when required. In fact, a majority of the backend of v4 was written in Python.

It's also interesting to note that most ex-digg engineers primarily work in a language other than PHP currently.