Ah thank you! That's actually quite a bit lower than I would've expected. Especially how it lags behind the rest in write perf.
Also found this geerling review [0] today (which mentions yours as well) which does list slightly higher numbers but he notes that he used actual thermal paste to get better cooling with that gaping heatsink box, which seems to have helped on at least a few fronts. If your cooling theory about the G2 holds, then the memory might be overheating on the X4.
There wasn’t any easy way to cool the RAM itself - in fact, I wouldn’t try to cool it using the same heatsink since the CPU would likely transfer heat to the RAM.
I suspect this is just a matter of timing tweaks in the BIOS.