FLoC was a proposal for targeted advertising ("how do you figure out who to show your ads to?"), and FLoC 2.0 is the Topics API proposal: https://github.com/jkarlin/topics

Mozilla's proposal here is for conversion tracking ("how do you figure out whether your ads are working?"). It is an alternative to proposals by Apple (https://webkit.org/blog/11529/introducing-private-click-meas...) and Google (https://github.com/WICG/conversion-measurement-api)

(Disclosure: I work on ads at Google, speaking only for myself)