Those Hyundai tests that Wuorela attended were likely very preliminary, could be just tests to see what happens to the car when they run jumps, and they were absolutely not allowed to crash the car.
At the same time, it's completely expected that Rally1 cars will have slower corner speed than current WRC because of less aero and simpler transmission. As for comparing to R5, that type of cars weren't present in the test that day, and even if they were, it would be questionable if anyone can judge cornering speed just by watching.