Generated schema contains "Record<string, any>" even with "additionalProperties: false" in openapi.json

[De4dVo1ce]

What problem am I facing?

Background

Hello there,
I'm building an application with a react frontend and C# REST API backend.
In the backend, I'm basically using dtos the following way (simplified):

// PersonDto.cs
public abstract class PersonDto
{
    public required string Name { get; set; }
}

// ChildDto.cs
public class ChildDto : PersonDto
{
}

// AdultDto.cs
public class AdultDto : PersonDto
{
    public required PersonDto[] Children { get; set; }
}

The generated openapi.json looks like this:

{
  "components": {
    "schemas": {
      "AdultDto": {
        "allOf": [
          {
            "$ref": "#/components/schemas/PersonDto"
          },
          {
            "required": ["children"],
            "properties": {
              "children": {
                "type": "array",
                "items": {
                  "$ref": "#/components/schemas/PersonDto"
                }
              }
            },
            "additionalProperties": false
          }
        ]
      },
      "ChildDto": {
        "allOf": [
          {
            "$ref": "#/components/schemas/PersonDto"
          },
          {
            "type": "object",
            "additionalProperties": false
          }
        ]
      },
      "PersonDto": {
        "required": ["name"],
        "type": "object",
        "properties": {
          "name": {
            "type": "string"
          }
        },
        "additionalProperties": false
      }
    }
  }
}

My openapi-codegen Problem

Now, when I run the code generation with this json, the generated schemas look like this:

export type AdultDto = PersonDto & {
  children: PersonDto[];
};

export type ChildDto = PersonDto & Record<string, any>;

export type PersonDto = {
  name: string;
};

My expectation was:

export type ChildDto = PersonDto;

Questions

Is this the correct behavior or really a bug?
Is there a way to configure this behavior?