Different works for an aria as part of the opera and standalone song?


There seems to be an ambiguity about works that can be used both as arias and songs (here an example by Gershwin: https://musicbrainz.org/work/8812f327-e92e-37b9-bdc4-2cc1ade322c8 and https://musicbrainz.org/work/0eca66d4-e4fd-3beb-bc1e-b2870d273f9d ) .
Should those be merged? There is a little discussion here: https://musicbrainz.org/edit/51124891 .
Since not everyone seems to agree on this, I thought I would put it to the attention of a broader audience.


Are the melody, accompaniment or lyrics different?
If only the arrangements differ, it should be the same work.


The Wikipedia article of the ‘song version’ states:
"It Ain't Necessarily So" is a popular song with music by George Gershwin and lyrics by Ira Gershwin. The song comes from the Gershwins' opera Porgy and Bess (1935) where it is sung by the character Sportin' Life, a drug dealer, who expresses his doubt about several statements in the Bible.
Now I don’t know if ‘comes from’ justifies a new work or on the contrary that the works be merged. I don’t personally know the works, but it seems like both have a huge variety of performer types, from the few versions I opened.