Ok. That's a more accurate representation of the gpu's performance in game. As already mentioned earlier, gpu boost clocks are affected by temps.
59 and 73C is pretty darn significant, as far as gpu boost clocks are concerned - 20 series is temperature sensitive. I wouldn't be surprised if your 2080Ti dropped over 100mhz between those 2 numbers.
My 1080Ti drops like 50mhz between 55 and 60C; 2000 down to 1947mhz.
Hmm...
What I think I'm seeing here:
-You both have the same cpu, but you have a 1080p 144, and they have 1080p 60. Even though you have the stronger cooler, I would not be surprised if your bud's 3900X is boosting higher than yours.
60hz does not require as much cpu muscle as 144hz, so theirs is likely hitting the 4.6ghz max...