You don’t need a spacer, I don’t know why it says that unless the older KH frames needed a spacer (I know the summit does) and it just hasn’t been updated in years.
I have a 27.2 thomson post and it fits perfectly in my KH frame.
The KH muni comes with a rail adapter, that isn’t what they mean by spacer though.
If you are getting a thompson seatpost, you are most likely not a cheapster.
I would suggest getting a Scott Wallis DeRail base that works amasingly with the thompson post (no need for rail adapters). He also has a lot of other goodies.
The Wallis DeRail base is awesome, the attached post is really sturdy even though it only has 2 bolts. A DeRail base with thomson post is pretty much the strongest seat/post combination you can get.
The DeRail base is designed to distribute the force from the post throughout the whole base and it is specially made to take the bike post, it probably wouldn’t work as well with the other kind of CF base. I actually asked Scott about that a long time ago, I don’t remember exactly what he said but I think he said it probably isn’t a good idea.