This is a fairly minor bug, but the GML export seems to use part_emitter_stream regardless of whether I have stream checked in the tool

Can it be updated to use part_emitter_burst if I have stream unchecked?

Yes you can.. (now) ... 1.5 supports both the burst and streaming option when you export. The export has been moved over to a tab.  if you are doing GML there is no change, just it's located on the side now