it says in the page that its because all the mails were on the same page (and presumably then scaped by the same bots), and yet a couple mails were recieved by

it says in the page that its because all the mails were on the same page (and presumably then scaped by the same bots), and yet a couple mails were recieved by other addresses and not by the unprotected one. So it would seem that the control is the set of unique mails recieved by all addresses. "Surprisingly, the unprotected email address appears to have blocked a spam email. Either that message wasn’t received, or an extra message was sent to one of the protected email addresses."