your benchmarks really leave questions and i can only guess some things. either the benchmark tool has some fluctuation or your mainboard has. Overclocking is generally not some good comparing example and needs good cooling and quite a lot of knowledge to make those "numbers" practical, stable and useable. I read much about overclocking, but if it comes to real life situations, my experience is that a overclock that works in benchmarks, quite often doesnt work with CPU demanding applications and i dont count games as very CPU demanding. 4,5Ghz sounds very edgy to me, if you dont have at least watercooling on your CPU.
I can overclock my i7-5960 easily to 4,5Ghz for example and i passed through the asus benchmark tool, hitting place 19 in the hiscore-list of the RoG-Asus website (for my CPU), but in no way i can run that stable 24/7 with i.e. Adobe Premiere or After Effects. I am pretty sure, that if you really stress-test your CPU (with CPU-Z for at least 2hours), you will get a BoD quite fast.
How about a test with a slightly less overclock, like 4,2 or 4,1Ghz?