Reference? Sure, I'll give you a reference.

A productive worker? Yes, I'd say he is. He's productive in the sense that a healthy sinus cavity is productive of mucus: the slow, steady dependable flow traps whatever random particles of work happen to be floating around the vicinity, and then slowly, creepingly carries them forward until eventually the finished product reaches a form where it can be expelled in quantity, and put on paper.

Or in this day and age of course, perhaps something more convenient than paper, for the output. Such as an electronic format, which for the purposes of our metaphor, let's call that a shirt sleeve.

Point is: this guy's productive.