I mean in the sense that he is storing pixel sizes as opposed to some semantic information. This implies either:

1. An elaborate system of decoupling styling information from content via metadata. (i.e. in situation X, this document's headline should be 20px) Their approach would be pretty interesting here. How could this be preserved as their design/layout evolves with time?

2. He was just indicating that headline in position X be 20px, communicating with the layout.

3. He was hard-setting it to 20px.

It's probably #1. So if, as he says they switch layouts and output to tumblr, how would that work? Their answer might be a lot of manual work, or it could potentially be something really clever.