I learned some interesting things this morning at my nearest dealer. Anderson Plywood in Culver City, Los Angeles.
Looking at the 'backing pad' on a new ETS -150, the pad does not bear a standard Festool P/N. Instead, it has a number close to what I have on my older sander, starting with PA 66.
Even so, the pad on my older RO 150 E+ is a medium foam-backed pad nearly identical to the replacement. OK for polishing and light sanding. The fellow at Anderson told me a few things about my sander, and Xeroxed pages from the Festool 2005 catalog pertinent to my machine. The accessories offered then have the same P/Ns as current accessories to the ETS-150. No difference.
He told me that his customers often ask if he has the older model sander available, either new or used. Of course he doesn't. Even though it has a 500w motor as opposed to the current 800w model, his customers like the balance and handling of the old one. Go figure! Weight seems about the same, although mine is considerably taller.
The user document you provided in .pdf format says that for polishing, speed 6 is desirable. That seems odd to me. I always polished and buffed out cars at lower speeds, and assumed that was standard industry practice. So, in all, I am back on track and happy with my machine as it is. With the addition of a sheepskin buffer pad.