[BUG] multipart/form-data in Swift URL instead of Data

This part:

"requestBody": {
          "content": {
            "multipart/form-data": {
              "schema": {
                "type": "object",
                "properties": {
                  "Trekk": {
                    "type": "string",
                    "format": "binary"
                  }
                }
              }
            }
          }
        },

generates

open class func adventuresUploadTrackWithRequestBuilder(id: String, trekk: URL? = nil) -> RequestBuilder<String> {///}
and then inside that it generates

let localVariableFormParams: [String: Any?] = [
            "Trekk": trekk?.encodeToJSON(), // json?
        ]

Adding --global-property skipFormModel=false does not do anything.

Start from the Swift operation entry point adventuresUploadTrackWithRequestBuilder and reproduce the multipart/form-data example with skipFormModel=false. Trace how the binary Trekk field is represented in the generated request, then verify that the generated client uses the expected data type and form encoding instead of URL JSON encoding.