organization is memberOf organization

[smrgeoinfo]

in the book, at https://book.odis.org/thematics/expinst/index.html#example-institution-graph

have

"@id": "https://index.example.org/id/org/x",
    "@type": "Organization",
...
    "name": "Organization X",
     "member": [
        {
            "@id": "https://example.org/id/org/1",
            "@type": "Organization",
            "name": "Organization A",
            "description": "Org A is a potential parent organization of Org X"
        }, ...

Isn't that supposed to be memberOf? (guessing that the intention is something like 'org X is part of Org A')