My questions about FLoC are who controls the definitions of cohorts? Is it possible for someone to take advantage of cohort information in a way which leaves Go

My questions about FLoC are who controls the definitions of cohorts? Is it possible for someone to take advantage of cohort information in a way which leaves Google completely out of the loop? Do users (and system administrators) have any control over what cohort information is saved or transmitted by the browser? If they do have control over it, is it enforceable? (e.g. The DNT header is useless because services are not compelled to obey the request.)