Usually LilyPond considers the octave of the last pitch it sees, which is sometimes confusing in polyphony.
However, with \choice LilyPond only "sees" the music expression that is actually chosen. That means that in \relative mode there is a problem when the different choice music expressions end with a different pitch.
I don't know how to approach that. If there is no reasonable way to ensure consistency (e.g. by injecting an octave check after the music expression) that limitation has to be documented
Usually LilyPond considers the octave of the last pitch it sees, which is sometimes confusing in polyphony.
However, with
\choiceLilyPond only "sees" the music expression that is actually chosen. That means that in\relativemode there is a problem when the different choice music expressions end with a different pitch.I don't know how to approach that. If there is no reasonable way to ensure consistency (e.g. by injecting an octave check after the music expression) that limitation has to be documented