Well I thought it’s obvious I agree with your idea in general, I am just saying it’s not completely the same from all points of view as you are making it look like, maybe unintentionally. 
Taking into account ONLY the immersion? Then yes, the same would apply on workers as well. But the more important thing is, that your worker sleeping instead of being at bench won’t have any real impact on your gameplay, if the resting spot is not more than 50 ft from the worstation. Because of this thrall missing at his station you won’t lose your stuff like you could, if your fighter would wander away from some area that needs to be guarded. Even when your worker thrall is not at his bench, you are still receiving bonuses, so it’s purely cosmetic. Though indeed it might be annoying, that they often seem to rest and chill, than to be actually doing their job. (here could be some option of adjusting how often will the thralls rest, or just shortening the times and frequency they do so)
In case of fighters, it is not only cosmetic/immersion issue, because there can be consequences of them not staying where you intend them to. And that is also why I say this function should not be there for fighters as well without the option to switch it on or of. In this case it’s not only about complaining that it does not feel or look immersive or real enough, because some types of thralls are excluded from this system. In this case you really are at risk and it would be silly to demand including them while not taking the possible risks into account.
I hope I made it clear enough now. ^^
I think that player who wants to find way to justice it for himself, so it won’t be ruining his game experience will do so any means necessary. Unlike a player who would be forever dissatisfied and impatient about possible changes (which might not even come) on principle, when the system is still developing. 
You can take it for example the way, that you told your worker thralls to be working in their own pace and take a nap whenever they need to, so there is the quality over quantity aspect. Meanwhile fighters have literally no other purpose than to be guarding. So they understandably won’t get the same space and benevolence as your workers, who have another types of purposes with it’s own pluses and minuses. You can also take some of your fighters from time to time, and put them manually into the bed, on the chair, so they chill as well.
It’s not much, but it’s better than to be sour about stuff one has no control over for now, just because.