It might be, it might not be. AMD set a lower baseline for 4 sticks so presumably some CPUs can't make those speeds.Thanks all. Well that kind of sucks, so my CPU is also a problem? I think I'll leave them stock, everything runs smooth so what's the point in risking instability.
Either way, XMP won't be optimised for 4 sticks and is unlikely to work with one-click, so at the very least you'd have to do some manual tuning as Sonic suggested.
If you can hit something in the 3000 region, most of the performance loss will be minimised. Running memory at a base speed like 2133 is to be avoided on Ryzen.