This bug has existed since the very first snapshot of 1.8 but I haven't heard anything about it on the bug tracker.

I can assure you it is real, i was in a village which had a single blacksmith (building) in it, and all the villagers that should have been brown-robed (to correspond to the regular huts) were instead black apron villagers (blacksmith).

If this bug isn't occurring for you, then one possibility is that you're village doesn't have any special buildings like butcher-houses, blacksmiths, churches or libraries, in which case things SHOULD be fine but I haven't found a village like this.