That's what I meant by "controlled experiment." I assumed from your answer that the saddle was the same.

Anyway, in case you're interested, with that one-bolt fitting on my SR post, I use a bit of silver antiseize on the bolt/nut threads and the surfaces of the curved washer, and a tiny bit on each of the rail holders. You can clean off excess with isopropyl alcohol. It really helps prevent any unwanted binding, but doesn't make anything slip. I also use it on the seatpost/seat-tube. Better than grease, any day!

Just don't get any on your fingers and accidentally transfer it to the leather saddle, because it'll be hard to remove.