I was under the impression that you could NOT use a Shimano Freewheel in conjuction with Suntour Accushift shifters?

Just for giggles I removed the Suntour 4 prong freewheel 1988 original 13x26 and spun on a Shimano 600 freewheel MF-6208 13x24 and it shifts flawlessly in Index mode with no adjustments at all? Is there something different about this Shimano Freewheel as compared to others?