24bit operation is definitely supposed to happen. A bug somehow got into the sound filing system routines some while ago (probably because of general code updates getting crossed in the post), which made all output revert to 16 bit as reported. I have completed a full rebuild of all programs which resolves this, restoring the intended behaviour, and I hope to have these available within the next couple of weeks (I am about to be away for a week) on the CDP website, with revised sources in due course on github.
The intended behaviour is for the output file to match the format of the input file, so that e.g. 24bit input gives 24bit output; with the option to force the output to floats using the -f prefix.