A little research seems to indicate that that is what Goodyear and Toyota would like you believe. Apparently any DOT approved tire the right size will work. Toyota (and Goodyear) want you use low rolling resistance tires, for better gas mileage and improve profits for Goodyear and Toyota dealers. Another compromise you need to make with a Prius - sacrifice performance (traction, comfort) for gas mileage.
Low resistance, high-center of gravity with all those batteries, a recipe for disaster on curvy roads. Sticky high-resistance tires are great for racing and making through curves. Gas mileage not so great, but fun on high speed romps.