Cars - Forsberg Racing Nissan 'Gold Leader' Datsun 280Z - Engine noise drops past 9k revs

This could very well be my ears deceiving me, but with the Race Camshaft upgrade on stock motor, in chase camera, there is a gradual drop off in engine noise when you go past 9000 rpm.

I noticed that to and the 2021 countach is like that to, possibly other new cars? Stock motor. Hit redline or past and engine sound gets quieter.
Think they was trying to simulate valve float…?