What progression did you use to sharpen the REX 121 Clay. If those are carbides, something you used sure looks like it flattened and smoothed them out.
I can’t tell for sure, perhaps the depth of field, but it really looks like there are scratches in the background material that just do not continue onto the carbides, but resume on the opposite side…
I’ll have to double check but I’m pretty sure that it was standard diamond plates through 1000, then core leather strops to .5um and then kangaroo strops to .25um.
I’ll examine the original photo more closely in the morning to look for what you’re describing.