Using fuzzy math would this mean that while the block was almost 600% difficulty, we were only paid as if it were 500% and that other 100% was not paid shares? [maybe a gross and missleading point, not sure]
Yes, - in fuzzy math, when there are greater 500% blocks, you have some work you did that's not paid, as its outside of lookback range.
However, those are rare. (Understanding we have a few in the past 9 months, but statistically over a long period of time they'll be exceptionally rare.)