Codec 2 good for voice, but not so much for CW

I’ve been thinking about making a kind of “codec2 robot” that people can telnet to and get responses from, and toward that end, I thought I’d see how it did on synthetic speech, since I thought being able to use a speech synthesizer for responses would be good. I had a file generated from my “mscript” Morse code tutorial generator thingie lying around, and passed it through Codec2.

Original sound clip, voice generated on MacBook, downsampled to 8khz.
Compressed via Codec 2.

It’s quite starting, but the segments containing morse simply disappear. I’m not sure I’d call that a flaw, but it may limit the usability of the codec in certain cases (like the CW practice nets held on some repeaters). Does anyone know if D-Star/AMBE does a similarly bad job of reconstructing these relatively pure tones?

Just curious.