Any question answered...

Aluminium seatposts seize in steel frames because of corrosion (electrolysis and all that).

That should not happen with carbon, as the carbon & epoxy is relatively inert.

It may seize due to physical reactions (if the epoxy swells, for example).

In any case, getting a stuck carbon seatpost out would be a piece of piss - A hammer and chisel would make short work of it.

Indeed, though Alu seatposts can seize in carbon frames, and that really is a fucking pain to shift.