My 1979 Miyata 912 with the Shimano 600EX arabesque group had the first (6-speed) cassette I’d seen, and the catalog from that year shows all the other Miyatas with freewheels. The 1983 catalog, now including Aero and Pro Miyata race bikes, still had freewheels on all except the 912, still the only model with the 600EX group and cassette.