Yes, there is a requirement to counsel. However the failure to counsel in a timely manner does not impact the flag action nor should it typically have a significant impact on a complaint.
Extract of AR 600-8-2 Follows
The flagging authority, unit commander, or first line supervisor will counsel all Soldiers on active duty, in writing, upon initiation of any Flag within 2 working days unless notification would compromise an ongoing investigation. Soldiers not on active duty will be counseled regarding initiation of a Flag prior to the conclusion of the first training period following the date the Flag was initiated. Counseling should include reason for the Flag, requirement for Flag removal, and action prohibited by the Flag. All flagged Soldiers will be provided a copy of the DA Form 268 when the Flag is initiated and when it is removed.