I am too little involved to invest the time to submit the bug report in a proper way, but
maybe there is someone around who just cares about this issue I'm posing.
The specs in
of JSR75 say that "The reason code for exceptions created with methods other than
PIMExseption(String, int) are set to the default value of GENERAL_ERROR."
At the same time the source code from phoneme_feature-mr2-rel-src-b23-08_may-2007.zip
in the file
sets the value to 0 (=FEATURE_NOT_SUPPORTED).