I've run into it too. Very difficult to get them to do it and seems to be luck of the draw. I had one quote me the rules as well which clearly stated connection point cannot be changed. However the last time I emailed the central concierge it was done without any pushback.

AC needs to clarify the rules, it's a very frustrating experience. Especially when WS same day change has no restrictions (add stops, remove stops, change route, all no problem) and is super easy to do (just call the regular call center).