Currently, the description of the "Soundtrack" Work type says this:

A soundtrack is the music that accompanies a film, TV program, videogame, or even book.

I would propose this clarification, taken from STYLE-193 which created the type to begin with:

A soundtrack work is a container for the individual works of music that accompany a film, TV program, videogame, or even book.

This more strongly implies, explicitly within the edit page (if the editor has "help" toggled on), that the Soundtrack work is supposed to be linked to individual works using https://musicbrainz.org/relationship/ca8d3642-ce5f-49f8-91f2-125d72524e6a

Alternatively, maybe the type should be renamed using the wording from https://musicbrainz.org/doc/Style/Specific_types_of_releases/Soundtrack#Work of "Complete Soundtrack"?