I thought it was pretty clear - he used "complect" because it shared an etymological root with "complex". The whole talk is about drawing distinctions between superficially related concepts, and using specific definitions based on words' etymological histories to do it.

The word "complicated" is generally synonymous with the word "complex", but that doesn't matter - the word "simple" is generally synonymous with the word "easy", after all. If Rich Hickey had said "complicate" viewers may well have asked whether he meant "to make complex" or "to make complicated", and perhaps wonder whether he was trying to draw a distinction between those concepts as well.