OData Reference URIs in request body

Take the following entities with a one-to-many relationship between Parent and Child:

public class Parent {
    public int ParentId {
        get; set;
    }

    public virtual ICollection<Child> Children {
        get; set;
    }

    public Parent() {
        Children = new HashSet<Child>();
    }
}


public class Child {
    public int ChildId {
        get; set;
    }

    public int? ParentId {
        get; set;
    }

    public virtual Parent? Parent {
        get; set;
    }
}

I'd like to create one new entity of both types within a single changeset and have the child linked to it's parent by using the reference URI "Parent@odata.bind": "$1". This is an example request:

Content-Type:application/json
Accept:application/json
OData-MaxVersion:4.0
OData-Version:4.0

{
  "requests": [
    {
      "id": "1",
      "method": "POST",
      "url": "http://localhost:5254/odata/Parents",
      "headers": {
        "OData-Version": "4.0",
        "Content-Type": "application/json;odata.metadata=minimal",
        "Accept": "application/json;odata.metadata=minimal"
      },
      "body": {}
    },
    {
      "id": "2",
      "method": "POST",
      "url": "http://localhost:5254/odata/Children",
      "headers": {
        "OData-Version": "4.0",
        "Content-Type": "application/json;odata.metadata=minimal",
        "Accept": "application/json;odata.metadata=minimal"
      },
      "body": {
        "Parent@odata.bind": "$1"
      }
    }
  ]
}

The Post(Parent parent) action method of the ParentsController always returns a new Parent object with ParentId set to 123. I would expect the Child object passed in as parameter to the Post(Child child) action method of the ChildrenController to have a nested Parent object. Although this is the case, the ParentId property value of the nested object is always 0 instead of 123.

Expected:

{
	ChildId: 0,
	ParentId: null,
	Parent: {
		ParentId: 123  // <----- expected
	}
}

Actual:

{
	ChildId: 0,
	ParentId: null,
	Parent: {
		ParentId: 0  // <----- actual
	}
}

If you use a full qualified url like 'http://localhost:5254/odata/Parents(111)' instead of $1 in the request the id is extracted correctly and available through the parameter object. This makes me believe that there is an issue with the substitution of the placeholders with the concrete urls from the content-id map. I traced the calls down to the method ODataJsonLightDeserializer.ReadAndValidateAnnotationStringValueAsUriAsync():

internal async Task<Uri> ReadAndValidateAnnotationStringValueAsUriAsync(string annotationName)
{
	string stringValue = await this.ReadAndValidateAnnotationStringValueAsync(annotationName)
		.ConfigureAwait(false);
	return this.ReadingResponse ? this.ProcessUriFromPayload(stringValue) : new Uri(stringValue, UriKind.RelativeOrAbsolute);
}

ReadAndValidateAnnotationStringValueAsync(annotationName) returns "$1" and ReadingResponse is false for my request. So a new Uri "$1" is constructed, which is not a valid OData Uri an does not contain any entity key. I suspect that to be the reason why I always get the default value 0 for the ParentId property.

If I change the code to execute this.ProcessUriFromPayload(stringValue) it returns the desired url "http://localhost:5254/odata/Parents(123)" and the ParentId value is set to 123.