That user number is not reproducible last time I tried (~8 months ago). I was looking at the code the other day and saw what I believe is one of the reasons, but I still couldn't find several million accounts (>10%), which is pretty hard to lose. (8+ bsky run pds equivalents)
This also does not account for (1) people with multiple accounts (labellers, feeds, bots, intent) or actual activity (significant % are likely churned, didn't delete)
