True statement(s). However, Kellerbier has become very popular in bottles of late, where you will find it carbonated to fairly normal beer levels (maybe just slightly less), whereas on tap it is less so, but what I have found in my travels (drinking) is that most places serving Kellerbier are serving more conventionally kegged versions than the traditional cask style.
So I think the carbonation level can be adjusted to personal preferences without being way off base for what you are likely to find in Franconia. Just keep it on the lower end of "normal".