Yes if you stabbed the throttle hard enough they would open for a brief moment as the engine vacuum drops but would close back down as you back out of the throttle before you tach out. There is a little bit of lag in the system as the valves move and how much movement you get between revs might not be real noticeable.
Hope that answers the question. Maybe this video will show the relationship better than i can explain it. Toward the end there is a slow rev to 3000 rpm with high vacuum (no load) versus the other quick revs (load).
https://youtu.be/RRXKdBR78Vw
So to recap with this setup: (non-factory NPP) in normal operation with vacuum applied to the system, there is variable positioning of the exhaust valves when the vacuum level is between 10 - 0 inches. Starting to open at 10, half way open around 5, full open at 0. At idle you are around 16-17 inches of vacuum and under
deceleration 24-26" to give you some reference values. So if you are revving at idle, you could only give a little rev and hit 7", a little more and hit 3" with the valves moving the appropriate amount. But you are only there briefly as you let off the gas for the next rev. If you want to make more noise, install the vacuum switch and break the circuit so the valves are open.
If you do not have a vacuum gauge in the car, all of these numbers are probably nonsensical but hopefully it explains the relationship on how it functions.