I believe it is mostly a motherboard limit. On top of this there is a silicon lottery among b-die chips (and this particular kit you got is known to be petty good).
You are at limits for daily of both vdimm, vccio and vssa, so I would eventually play only with subtimings to squeeze a little more in benchmarks and 0,something% in real world applications then call it a day
new rig 2019:
Intel 9900k >5ghz | Asus Maximus XI Gene | Eisbaer 360 LT (custom loop in progress) | bequiet! Dark Base 700 white edition | Team group Nighthawk 16GB 4000mhz | MSI RTX 2070 Armor | Storage: Intel Optane 900p 280GB + Samsung 970 evo plus 1TB + WD Red 3TB | Corsair HX850i | Benq BL3200PT 1440p | 1Gbit ftth |