Having read some of the comments in here I'm surprised to see that no one has mentioned how the co-workers reporting their time are lying and this developer isn't. If you worked on a feature for an hour and stared off into space for another hour you report that the feature took two hours. If you took 30 minutes to write an email you certainly don't report that; you move time around to make it look better.

This behavior is totally normal in this industry and if you get put in a situation like that you have to do the same. No one can concentrate for 40 hours every week on development without getting burned out.

The reality is most people are probably lucky to get 20 hours of productive work done a week.