Yeah it runs hotter, but that basiclly depends on what mosfets they have used.
IR powerstages or Ti nexfets have a very decent efficiency traditionally.
Even at temperatures above 120°C.
But those you will mostlly only find on the semi to higherend boards.
With cheaper boards you often find lower quality fets that have a good rating untill a certain temperature, then they often start to degrade in efficiency pretty quicklly wenn passing said temparature rating.
Next to that with 4+2 it basiclly has less phases, so those will allready run warmer from the get go.
So yeah thats less efficient basiclly.
However for a general user they would probablly not really notice much of that.
And its still a matter of how high the cpu will overclock in the end.
But diehard overclockers and tweakers will probablly notice the diffrence.
Anyways yeah 3.8 to 3.9 is indeed pretty suprising for a board like that.