category community - need to adjust the membership. Access groups not updating

Summary: category community - need to adjust the membership. Access groups not updating

Content (please ensure you mask any confidential information):

We have some category communities set up with ad hoc person criteria. We wish to adjust this (for a list which is smaller).

There appears to be no ability to delete or end date an access group (despite "stop date" being a column). Adjusting the current access groups also appears to have no effect - I've changed the criteria for an access group from a person criteria holding >9000, to just a single individual - myself.

Despite reconciling the access group is still showing the original >9000 users. Is this expected?