I attended that same convention/session and concur; it was also cool to meet Bob Gurr in person.I attended the Retro Magic convention at Beach Club last month. Retired Imagineering Legend Bob Gurr told us that he was brought in to look at issues with the track system before Epcot opened. He evaluated all the options available at the time and told WDI that buying wheels by the truckload would be more cost effective and reliable than the other options.
Can't wait for the next RetroWDW event (I think they said a couple of years)!