It’s a limitation of 2DPC topology. Vermeer’s DDR4-3200 1DPC and DDR4-2667 2DPC, for example. Intel’s mostly more restrictive than AMD (what Intel calls 1DPC everybody else calls 1SPC).
You can find my y-cruncher default here. I’ve also had OCCT pick up errors pretty quick but y-cruncher’s had consistently faster time to detection with DDR5 2DPC 2R. So far Prime95 blend or long hasn’t picked up anything that’s gotten through y-cruncher and OCCT for me.
Depending on HVAC it can take several hours to run DIMMs up to peak temperature. So a full temperature sweep can take a while.
I’ve tested on AGESA 1.1.0.0 to 1.2.0.3e. It’s made exactly zero difference.