A couple things different you are doing than I:
I will try on an open dwg and see what happens, but its not really a case I care about. I always run on dwgs not open in the editor.
If it is the regapp cleaning step that is causing the recover thing to show, you can imagine that is a strong argument for not running the purge using an in process method. A standalone exe does not even know acad is running, so will never stop a process, it will suceed or fail, exactly what people running batches want.
My tools check file sizes and change dates to see if tools are working, they do not need to get return values or errors from the purging mechanism.