I’m unclear about when a soundtrack should be a work rather than just a release. I came upon this issue when tagging Beethoven’s 6th, which confusingly said that the top-level work was Fantasia. It doesn’t seem to me like Fantasia should exist as a work at all, but I couldn’t find any clear guidance about that. I’ve been unable to listen to the only recording linked to the work, but it appears to be an arrangement of some combination of the works in Fantasia, obviously not a complete recording of Fantasia.
A soundtrack work is not the same thing as a soundtrack release.
The “soundtrack” work for a movie like Fantasia is a collection of works used in a film, game, TV series, etc. Use of the “part of” relationship for this is consistent with the style guidelines for soundtracks.
A “soundtrack” release is an actual medium with specific tracks and recordings, such as a CD. Often such releases don’t include absolutely everything (although Fantasia is probably a special case ).
In most cases I would say it does not make sense for recordings to link to “soundtrack” works, but rather should be linked to any and all actual works that are performed. However, this may not be easily knowable in which case it could make sense to link to the soundtrack itself.
According to the Japanese wikipedia of Fantasia, the total time of Beethoven #6 in Fantasia is 22minutes and there are several cuts except for 4th movement. So I don’t think it is a part of Fantasia.
If Fantasia should exist as a work, my opinion is to add a new work of Beethoven #6(Fantasia arrangement by Stokovsky) which is an arrangement of Beethoven #6 and make it part of Fantasia.
If the Fantasia arrangement meets our standards for a separate arrangement work: publication, multiple performances, etc. (I suspect this is very likely due to the nature of this film) then this would certainly be a reasonable course of action.
However in general just because only part of a work is used in a movie would not be sufficient reason by itself to create new works just for inclusion in a soundtrack IMO, as it fairly rare for complete performances of anything to be used in films (but may be on the soundtrack CDs).