Either this, or mount it ungreased. I guess in both cases this bike will start to creak much earlier than a regular one. If you grease it and keep it outside of the seat tube, a lot of dirt will stick to it which then makes its way into the seat tube. When it rains more water then usual getting in the bottom bracket area will be another challenge.

This is actually a bad idea. No upside to greasing your seat. At best it just makes it slip.

Source: Profession cyclist for the last 15 years.

Seat posts, especially of a different metal to the frame (e.g., carbon or alu seatpost in a steel frame), regularly seize in place without grease (from galling or corrosion). Often in a matter of months. I’m amazed you’ve never run into this or heard of the idea in 15 years of professional cycling. Did you ever work on your own bikes?

If you’re looking for more friction than grease, you can use carbon assembly paste. But either way, you want something between post and tube.

I've heard of it, we just don't do it.