While not offical there are also datapoints of a SDC from /to a co-terminal.
From my experience, as a 75K, coming from a confirmed upgrade on a SDC, I have been upgraded on the new flight without ever showing on the new flight upgrade waitlist, however I was unable to determine if my prior upgrade granted me higher priority. I have also done a standby to an earlier sold out flight while still confirmed on the later flight and did move to the top of the awaiting seats list and was cleared next.
AS customer service for Elites is pretty amazing. I think you will find that as a 75K you will see a favourable difference between what is written as policy and what you experience. I have experienced some incredible service that bent the rules so far it twisted them into a pretzel.
Welcome to AS and 75K.
James