message: Default engine is BPFile, i.e. as of today, for writing it is always a BP3 engine, for reading it is BP3 or BP4 depending on the file it is opening.
diff: @@ -463,7 +463,7 @@ Engine &IO::Open(const std::string &name, const Mode mode,
  /* BPFile for read needs to use BP4 or BP3 depending on the file's version
  */
  - if ((engineTypeLC == "bpfile" || engineTypeLC == "bp"))
  + if ((engineTypeLC == "bpfile" || engineTypeLC == "bp" || isDefaultEngine))
  {
  if (mode == Mode::Read)
  {
  @@ -482,7 +482,7 @@ Engine &IO::Open(const std::string &name, const Mode mode,
  }
  }
  - if (isDefaultEngine || engineTypeLC == "bp3")
  + if (engineTypeLC == "bp3")
  {
  if (mode == Mode::Read)
  {
  