I didnt see it mentioned, but what USB port/location are you using to test with?
I'm still using two of the original G Pro wireless (The superlight/X models had the issues with dying scroll wheels and buttons) with the powerplay mat, and found it's responsiveness is noticeably better with the physically closer receiver (Or the mat, which replaces the receiver right next to the mouse)
I've also had a few USB ports over the years cause issues with higher speed signals (1000Hz mode), where front-USB3 ports had issues while front USB 2.0 did not, the included extension would actually fix the issues on the 3.0 ports against the logic of 'shorter cable = better'
I can see the demands of this 2000Hz adaptor being tighter, location and port may be more critical than lower speeds?