The transmission is a tad slow to respond to
big acceleration requests, then sends the engine spinning high into the rev range while the CVT accelerates the car using its... continuously variable ratios.
Under normal use the engine stays impressively subdued, but
requests for
big acceleration - the sort that would get an automatic kicking down to its lowest available ratio - result in it accelerating to peak revs, resulting in a noise out of keeping with the character of the car.