Calling attention to (say) a 250-line neat hack - say a patch to a driver, or solving some elegant toy problem - would constitute a detraction from the programmers' major contribution at work over the course of years.
I view this new fixation on open source contributions as a continuation of the pathological distrust for programmers' skilled contributions that used to be expressed through high-stakes (or even low-stages) white-board coding challenges. I'm not sure which is more irritating.
You act like the code you've written that no one can see should matter to another company interviewing you. There is no way for a interviewer to verify the work you've done at your previous job. Like it or not, if you are looking for a new job it is your job to impress them. Fail to do that an risk them picking someone else.