This is in reference to https://github.com/metabrainz/musicbrainz-server/blob/82e585d/admin/RunIncrementalJSONDump#L26-L33

The comment there is outdated, because we now have mirror-only triggers which are in fact required in order to keep tables like `recording_first_release_date` up-to-date.

Recently I'd determined that this was the reason many recordings were missing first-release-date fields in the JSON dumps.