It's a simple question of when the rides were ridden (with any ECE taking the date of the host ride, even if the ECE was started before midnight).
The event shown above is dated 31st October 2020 in the Calendar data. Is that not when it was run? If not, was it an AUK event at all?
The ghost members are explainable as in a couple of posts previous. The auto-nightly results-fettling routine always runs on 'this' season, and doesn't fettle 'last' season. It will get run manually for last season at some point.
[edit to add - I've run the routine manually and the missing names are now all there.