Question about After Market Cards.

https://www.kitguru.net/components/graphic-cards/leo-waldock/asus-rog-strix-rx-vega64-o8g-gaming-preview/

 

The slide that is interesting to me, is the Firestrike extreme run showing average clockspeeds.  The ASUS Strix Vega 64 dips down to a lower clock speed far less often than the reference board.  Now, the question I have is, is that because of the improved thermals of the custom cooling solution, or is that also partially due to the custom built PCB and components used?

 

If you used a full coverage water block on the Strix PCB vs reference, would one be better than the other?

 

Anyone have any experience with that?