Since the World Map update, a little pop-up panel within the recruiting UI has advertised particular traits (“higher melee skill”, “higher initiative” etc.) that are supposed to be associated with a particular background.
Prior to that, I had already built up a strong working knowledge of which attributes were likely to be found from a particular background, and was therefore surprised to see (a) some attributes attributed to backgrounds that I had not noted to have them, and (b) some attributes not being attributed to certain backgrounds that I HAD noted to have them.
The best example is probably Gravediggers, who supposedly possess “higher max fatigue” and “higher bravery” (i.e. resolve). I keep recruiting them to test my theory, and they keep being thoroughly mediocre, with a max fatigue almost always between 100 and 105, and resolve usually in the 40s (often the lower 40s). As if to confirm my suspicions, the most recent one I purchased had the Fat trait (so that his max fatigue dropped from 102 to 87) and the Insecure trait (so that he would never be of confident morale)!
Millers are supposed to have high max fatigue, but they usually have around 105 and I’m not sure I’ve ever recruited one with over 110.
Thieves and Gamblers do have the higher initiative attributed to them, but it is also common for them to have a basal melee and/or ranged defence of around 10. This isn’t guaranteed, but it’s common enough that I’m very surprised when they don’t possess these attributes.
Jugglers do have higher initiative, and a hard-coded +5% chance to hit the head, but they also almost always have low hit points (usually in the 40s) and low resolve (usually in the 30s).