cr:containedId vs schema:isPartOf

[smrgeoinfo]

I'm wondering why croissant invented 'containedIn' and 'includes' for filesets. wouldn't schema:isPartOf and schema:hasPart work just as well?

E.g.

{
  "@type": "cr:FileObject",
  "@id": "train2014.zip",
  "contentSize": "13510573713 B",
  "contentUrl": "http://images.cocodataset.org/zips/train2014.zip",
  "encodingFormat": "application/zip",
  "sha256": "sha256"
},
{
  "@type": "cr:FileSet",
  "@id": "image-files",
  "containedIn": { "@id": "train2014.zip" },
  "encodingFormat": "image/jpeg",
  "includes": "*.jpg"...

Could be

{
  "@type": "cr:FileObject",
  "@id": "train2014.zip",
  "contentSize": "13510573713 B",
  "contentUrl": "http://images.cocodataset.org/zips/train2014.zip",
  "encodingFormat": "application/zip",
  "hasPart":{"@id":"cr:FileSet"},
  "sha256": "sha256"
},
{
  "@type": "cr:FileSet",
  "@id": "image-files",
  "isPartOf": { "@id": "train2014.zip" },
  "encodingFormat": "image/jpeg",
  "hasPart": "*.jpg"
}

[smrgeoinfo]

and the answer is... :)