I found the problem in the end: those aren't Ogg files, they're MP3 files which were just renamed to .ogg. NW.js can't play MP3 files but Chrome can. So in fact you must have incorrectly imported the files somehow, or did you think renaming the file would convert it? (It doesn't!)
This also explains why Asmodean's workaround works: you convert the MP3 to WAV, then re-import it, then C2 encodes a correct Ogg Vorbis file.
NW.js should always report useOgg = true in the console. I just double-checked this and it does. The dopplerFactor message is irrelevant.