Raise uncore to 4500 and see if it still passes...
In fact 5GHz is a good comparison point regarding temps... From the ones (35 pieces) we tested last week, the best that could do multiple runs of CB R15 (5000/4500 & mems at 3600) with a non fixated DH 15 was at 1.23Vcore on GB Z270X SOC. (Non delidded)
Average voltage was around 1.285Vcore
Massman has the Excel sheet