they hate reciprocating loads
YES!
The needles don't rotate, they only oscillate (pendulum swing), with the same 10 or 12 needles (looks like 33 or 34 may be the maximum # of needles in a full-complement bearing without separators) around 12 o'clock taking all the compression load without developing the hydrodynamic wedge (as between the mains and MB) that saves the journal from making hard contact.
Using 2 bearings isn't to increase load capacity, it's to prevent that tiny needle from cracking in half by bending. Harley learned that the hard way 60 years ago.
Any sign of local fretting inside the rocker body near the edge of the roller?
You mean like what happened to my rear u-joint? The rollers sit in the same spot and just eventually wear it out. In this case the needle rollers are harder than the shaft material, so they win.
