On the stock ST's shock, yes.
But the question was about the rebound damping, the only adjustable damping on the stock ST. I would not adjust the damping because of the pre-load adjustment. I would increase it because of the increased mass. Remember: rebound damping is independent of the spring compression (it works on spring extension), so spring pre-load does not enter into the damping question.
The problem here is that as the stock ST's shock spring is too weak for the bike in the first place, so one has to make both adjustments. It seems as though one setting affects the other because of this. It does not. Point in fact: I have an after-market shock with a spring adequately strong (1,300 pounds) for a passenger, a rider, and gear. The sag has been set, both front and rear with this in mind. I do not need to adjust the shock spring's pre-load, even when adding a passenger. I do need to change the compression damping, though: more for more mass, less for less. Not much, mind you, but some.
As the rebound damping was adjusted for the spring rate and passenger + rider + gear mass, the rebound rate generally stays the same. Unless I want to go "bonkers" in the mountains. Then the rebound damping goes up one click. It goes back to the prior setting for freeways.
Hope that this make sense,
Marshal