Agesa 1007b for the ASRock X670E Steel Legend is buggy. My memory which is 6000MHZ and runs fine on the previous ROM doesn't work on Agesa 1007b for XMP1 6000. 1.26.AS01 is the rom that works fine.
1.28.AS01 doesn't work properly with Corsair Dominator CMT64GX5M2B6000C40
Both of those BIOs are beta so I guess bugs can be expected.