The other side is forced to agree to that, just to get a little.
That’s not how the ultimatum game works in non-CDT settings, you can still punish the opponent for offering too little, even at the cost of getting nothing in the current possible world (thereby reducing its weight and with it the expected cost). In this case it deters commitment racing.
LW doesn’t punish, it upvotes-if-interesting and then silently judges.
(Effort is not a measure of value, it’s a measure of cost.)