Seem to remember something about PIONEER raising hell over someone copying parts of the power supply of the SX-1280 or 1080, which ever had the toroidal transformer (NOTE: I looked up both and SX-1080 and SX-1280 and they both had Toroidal transformers) It's pretty fuzzy in my mind. Needless to say it was short lived and the offending units were converted to I-E transformers. As the RS-20xx series came out at the same time as the SX-xx80 series, it's a distinct possibility.
Pioneer used the toroidal first in the SX-1250 from the generation before x80. I never knew about them hassling Fisher, but they definitely went after Radio Shack for their Realistic STA-2100. Almost every sample you can find in the wild is actually STA-2100D with a standard xfrmr.
Did Pioneer actually have a case back then? The whole world can use toroidals now...