This is fascinating, but all the traces to what I have seen thus far point to every bit of truth you have spoken about above. I do not need to do a lot in 1.3 and I do not need to go further back than 1.3, though I do have an A500 with 1.2 ROMs, but understanding why things work the way they do is both fun and enlightening. In fact the main reason why I requested volume name to device name conversion was that I could only seem to find docs on getting the volume name. V36 up has so many more calls available for accessing things like this.
I will start a thread about message ports soon too and some of the weirdness I am seeing there. Thanks for such comprehensive answers.