Don't know too much about the SBX, but if it's like most of the systems I've encountered---I think you're on the right track.

You have to understand what's happening here, too. If that conf initiator DOES drop out, those people can stay on the line----forever. However, I'm also wondering (like you)---why the timer would kick in when all parties are still talking??

Someone who knows the SBX will jump in here and shed some light on this.