Very interesting analysis, thanks for sharing.
Beginning to think their block-explorer is lying...
https://explore.veriblock.org/network-statsAs that would imply 20ish endorsements per block. But when I scroll back over the last few 100 blocks looks more like 1 or 2.
Looks like the Endorsement Rate is now showing
2.23 / block on
https://explore.veriblock.org/network-statsIt could have been a bug, or perhaps it was a result of a lagging moving average calculation. I wasn't able to find any source code for their explorer at
https://github.com/VeriBlock so it's not clear how exactly they are calculating that endorsements figure they display.