The difference of 812 mVolts and 890 is only a AFR difference of about 12.7 to 12.5 AFR so not that far off.
Both sides of engine exhaust makeup rarely are equal

Add long tube headers and many times one O2 is at a different distance then the other sides O2 thus one reason for reported difference.

Cannot speak on that one wideband O2 as what it reports but again kinda half an answer since other sides exhaust has no wideband and what it reports.

PCM of course ignores the O2s for WOT but also the PCM only reacts to O2 values once a minute so a captured scanner recording of 45 seconds might not give a true AFR rate from 02s.

It is hard to see the lines in graph due to line colors and gray background but it seems once above 4,000 RPMs which is where PCM stops looking at MAF and more to VE that imbalance seen clearly.

It seems both have about the same switching rates, sometimes one head has better flow and thus imbalance seen as the exhaust rate speed up.