Hi, this could be happening for so many reasons...
Changing boards means different ways on how the CPU behaves and/or even how the fan curve for the Wraith Prism is adjusted. Among other things.
Better VRM design may also allow the CPU to go further than before or maintain a certain clock.
Its hard to say because there are so many variables, like used thermal paste. But, If you aren't getting like 80 to 90ºC during gaming, then you are just fine.
The Wraith Prism is a wonderful cooler, I had one for quite some time but If you really want sub 40ºC while browsing or doing average tasks, then a AIO Watercooler or a beefy Air cooler is needed.
The Englishman