This happens because Live uses the track names when importing a midi file. I don't think the track name can be changed in detonate. But you could rename the clip in Live (cmd-R) and export it as midi file. Thereby the track name will become the same as the file name. However, Live only exports single-track midi files (format 0).
Detonate by default gives format 0 files. But the point is that Live can also import format 1 midi files, where the different tracks from the file are stored as clips on different Live tracks. So it makes sense in Live to use the track names for identifying the clips. I think Live handles format 0 files just like format 1 containing a single track.