Updating linked object from GraphQL raises duplicate key error

In a relationship, there is

{
   link: objectId,
  **create**: object
}

BUT there is no

{
   link: objectId,
  **update**: object
}

When creating a new linked object, the linked object gets created fine BUT when updating the same object, GraphQL throws an error saying the _id is duplicated.
As an example, this works if the item does not exist

{
  "id": "626f2eec9d529fac10934538",
  "input": {
  "brands": {
      "link": "626f2eec9d529fac10934531",
      "create": {
      "_id": "626f2eec9d529fac10934531",
        "name": "Nike"
    }}
  }
}

BUT will fail if you try to update or upsert. It looks like Realm GraphQL only defaults to insert regardless of Update or Upsert. It makes sense to be able to update linked objects if I am allowed to create them .

Is there anything I am missing or is there no update for linked objects?

It will be good to get feedback from the Mongo Realm team on why they have linked relationships to only create BUT NOT update. I know the common answer is to use customer resolvers but seems like a standard workflow.

Just to sum up the above if you have defined a relationship:

 "brand": {
    "ref": "#/relationship/mongodb-atlas/products/brands",
    "foreignKey": "_id",
    "isList": false
  },

GraphQL will create

{
   link: objectId,
   create: BrandInsertOne
}

This allows you to insert a new parent object embedded with a linked object. BUT when you try to update the same object, you get a duplicate error on the embedded object.