According to the Discourse 2.4.0.beta11 Release Notes :
Suspect users sent to review queue
Suspect users - those who have viewed less than one post and one topic but have customized their bio - are now sent to the review queue. Such users have a high likelihood of being spammers, as most users browse the site before taking time to fill out their bio.
This doesn’t happen for us; new suspect users appear in /admin/users/list/suspect as usual, but not in the review queue. Does this depend on some settings?