It’s common for a label to intentionally release a soundtrack in separate parts (e.g., Vol. 1, Vol. 2…), and it would be the intention of the label that these are a soundtrack to a specific thing. Therefore, I don’t think adding “complete” is an accurate discriminator.
What’s been said by the Style Leader is more along the lines of,
A compilation of various recordings from unrelated soundtracks would not itself be a soundtrack - just a compilation.