Ross
I have seen some Inglis's and Kenmores at a later date agitating close to that speed, and I've also seen others of that make agitate slower, like about the pace of a Maytag or Speed Queen (approx 60 per minute). I think the WP BD system was built to agitate briskly, and they do at first, but as time goes on, they tend to get slower with age. My family's Inglis agitated approximately that fast, and it was from the 60's. At new, the WP BD agitation speed is comparable to an Electrolux/WCI/Kelvinator index-drive top loader, and a solid-tub filter-flo GE (approx 70 per minute). Perhaps the really old WP washers had a stronger motor than those of the later years, and were able to keep the pace longer.
Gary