Originally Posted by
Nerull
Carbon Assembly paste contains grit particles, which bite into the otherwise smooth and slick resin of the frame and seatpost, increasing friction. Grease contains no grit - or it wouldn't be very good at it's job. One is ment to increase friction, the other to reduce friction. They are not the same thing, and not interchangeable. Not if you like your saddle staying in place, anyway.
It's not just it's got grit in it. The paste I use, Tacx dynamic assembly compund I think it's called, seems to dry out after application rather than staying ummm greasy. I'd imagine this is exactly what it's designed to do, make insertion easy, then between the grit and the drying, create more friction than just having the naked carbon.
It's always why when I make adjustments, I'll remove the post wipe it down, re-apply assembly compound and refit.