[mceachen]

It may be a reference to https://en.wikipedia.org/wiki/Rule_of_three_(computer_progra...

The idea is that you grit your teeth and let code be deduplicated twice (but no more), rather than immediately DRYing up code, so you'll (hopefully) have a better sense of what the common code should look like.

(I personally think it's too hard in practice, as common code can be written sufficiently differently to not be recognizable as common by the Engineers Of Tomorrow).