Just a small clarification, server-side copy stats were not added as a result of this thread (B2 server side copy doesn't show cumulative progress - #12 by ctonsing)
As @ncw states in one of the responses (https://forum.rclone.org/t/b2-server-side-copy-doesnt-show-cumulative-progress/11154/13?u=ctonsing), "Relatively recently rclone started accounting for server side copies too", which was before I submitted the question.
I only mentioned a discrepancy in the stats which turned out to be an error in the stats accounting which was subsequently fixed.