Please see https://meta.miraheze.org/wiki/Tech:SRE_Duty for more information.
The person attending this event is deemed to be "on duty this week".
While SRE strives to announcements through email, not all services offer a security-only announcements mailing list. The person on SRE duty must check the announcements regularly, but at least once per week, and contact SRE in case of findings. The point of contacts are the people experienced with the service, and they can verify your findings.