Type boolean renders field with a truthy value, but no default value is specified in schema

[ferrykranenburgohra]

I have the following schema where a user must choose on or another. I'm not allowing a default value. It renders visually a radiobutton. I'm using version 6.0.0-beta.16. But since this version (6) there is a default value that breaks our logic.
The same happens on the demo site https://rjsf-team.github.io/react-jsonschema-form/

What am I missing?

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "required": [
    "nietAkkoord"
  ],
  "properties": {
    "nietAkkoord": {
      "title": "Ik ben niet akkoord",
      "type": "boolean",
      "oneOf": [
        {
          "const": true,
          "title": "Ja"
        },
        {
          "const": false,
          "title": "Nee"
        }
      ],
      "not": {
        "const": true
      }
    }
  }
}