I just know that when the change at the end of 2018 came, it was communicated that every esta would be reviewed by a human and automated reviews and insta-approvals are no longer possible. As a result, there was an end to the applications submitted one second that were approved the next.
You can read about it here: https://www.cbp.gov/newsroom/national-media-release/cbp-reminds-travelers-allow-72-hours-esta
Citat: ”Due to changes in ESTA application processing, real-time approvals will no longer be available.”
In other words, someone has worked quickly and approved your application. It is quite likely that a system still does the pre-review and a human finally approves in a call center somewhere, with the option of sending for extra review when needed.
Following with that announcement, CBP upped its use of automated batch processing for some additional checks/feedback and wanted to publicly make it appear as if the checks were going to be different than before — and they became so — by taking additional time to both do automated reviews with additional batch processes run on applicants and for more manual reviews.