Distiller: Watched Folders with prologue.ps

I've just experienced an odd behaviour when using Distiller Watched folders, with "Use prologue.ps and epilogue.ps" in the job settings for the Watched folder.

When working with Watched folders, Distiller does NOT use the "normal" prologue.ps and epilog.ps files in the Data folder, but instead requires its own set in the Watched folder (i.e. alongside the joboptions and In and Out folders).

If you don't have these files present, Distiller processes the job, deletes the .ps file, but produces NO PDF, despite logging that it has done so, and flagging no errors.

It's taken me a while to figure out exactly what was going on. I doubt than many will care, but it may help some other poor soul.

This is for Distiller X on OS X El Capitan.