It is increasingly common to see labels release a single recording as its own release on digital platforms.  These events are usually omitted from the artist/label's "official" discography pages.  These "advance delivery" 1-recording digital releases usually happen weeks or months in advance of the CD release of 4+ recordings.

Currently, these Song release groups and Maxi Single release groups are merged into the same MusicBrainz type "Single".  This causes editors to take a variety of questionable actions on the release groups that share names, such as:

• Merge the release groups, even though it could be argued that a 1-recording release is not a version of a 4+ recording release.
• Classify the Maxi Single as an EP, even though it is not.  (Apple tends to do this.)

Here is an example artist overview: https://beta.musicbrainz.org/artist/de220a71-1021-4eda-949f-2ff0ff2b79e5

This artist has 6 "Single" Release groups, 5 of which are Songs, and 1 of which is a Maxi Single.  It would be beneficial to separate the Songs from the Maxi Singles.