ok, I will tell you were it really helps!
I have bought asrock ab350 pro4 mainboard, cause I wanted to try ryzen cpu..
I knew that it was able to handle 6 cards, cause same board was handling 6 amd rx570 in my friend's house.
but sadly! when I instelled there 6 NVIDIA cards it failed... cause it can support only 3 nvidia cards... that was the case when this small extender saved me