That’s very true but we don’t have the data CCP has so we can only guess. I would think that multiple PI/skill farm alts would shift the statistics to fewer alts online at any time.
It also looks like I misremembered the graph:
(from https://www.reddit.com/r/Eve/comments/3j7nso/at_least_we_know_how_many_alts_there_are/ )