Congrats on spinning your witness node, BUT:

Their backups (21-50) process what they miss. And their backups, all the way to the 100s, process what the primary backups miss.

Sorry to say, but that's anything but correct! One backup witness is scheduled every round, whether the top 20 witnesses miss a block or not, and whatever their rank, even greater than 100. The higher their rank, the more often they will be scheduled. The concept of "primary backups [witnesses] (21-50)" is pure fiction!