@YetiChow Yeah, I agree with the core thrust of your argument. That’s why I’d be against a “Hates this job” style thought when the hearthling isn’t assigned to their main job or is in whatever is considered an “opposite” job.
That said, I think if not every hearthling has this trait it sidesteps most of your concern. I’m not particularly interested in having every hearthling have a particular job that they love - it’d only be a small proportion of hearthlings with this trait. Since there is no downside to having hearthlings perform whatever job you want typically and only an upside to happiness in a small number of cases, I don’t think this falls into the optimization trap you are worried about.