editor.FileDialog(eeFileDialogSaveAs, …) cannot select a read only file

The following is “unexpected behaviour” rather than a “bug”.
Example:

#language = "V8"
#async = "off"

// let nFlags = eeFileDialogNoReadOnlyReturn;
let nFlags = 0;
let sFileFullPath = editor.FileDialog(
  eeFileDialogSaveAs,    // nType
  nFlags,                // nFlags
  "ReadOnlyExample",     // strTitle
  "Text (*.txt)|*.txt",  // strFilter
  1,                     // nDefFilterIndex (base 1)
  "myReadOnlyFile.txt",  // strDefPath
  "d:\\example\\",       // strDefFolder
  "txt"                  // strDefExt
);

No matter how I set nFlags, I always end up with “try again …”:

My code can handle read only files, but I have no way to select the read only file for save.

Am I missing a flag?