Tim,
I think it is more to do with the 'kludge' in the way Winders handles USB, and tacks it into the Operating System and hardware via a 'virtual' COM port..
The documentation that comes with the Massoth PC Module could be better..
AND, all software tends to be only 'just about fit for purpose' these days.
I had the devil of a job getting my head round it initially. - In my case, I did not realise you used the Update Utility, rather than the DCC Programmer software, to (in my head) 'program' the XLS with the soundfile..
Once you have done a few sessions, it becomes second nature.
PhilP.