Being able to move tracks around in the track parser with all the information moving with them is admittedly pretty useful in a lot of cases. When there's a discID, though, you won't be able to change the order of tracks+durations, because that's mandated by the discID... but the track parser will still try (try to edit the track order in http://musicbrainz.org/release/6901edd8-4d0f-405d-81ab-369022d2df5b for example). This means you'll be blocked from advancing ("The length of track n cannot be changed since this release has a Disc ID attached to it."). This feature shouldn't be called when a medium has a discID, either just not working or allowing just to rename the tracks (which is the most likely reason why somebody would want to do such a change anyway when a discID is present)