Not sorted ascending:
https://beta.musicbrainz.org/ws/2/label/e206bbcc-7dce-4a2c-a30e-08494961c99e?inc=url-rels (2014.09 comes before 2006)

Sorted ascending (no months populated):
https://beta.musicbrainz.org/ws/2/label/dee62e1a-cfd1-466f-b578-846a0fdf435a?inc=url-rels (1991, 1998)
https://beta.musicbrainz.org/ws/2/label/7c614735-33ba-4bed-bbb7-89b7e72ce9bb?inc=url-rels (1998, 2002)
https://beta.musicbrainz.org/ws/2/label/c74f55dd-a0ef-4de1-b870-acc7e11a9959?inc=url-rels (2004, 2009)

(or, is it random chance what the ordering comes back as?)