Whitaker was Senate confirmed in 2004
http://web.archive.org/web/20041119045234/http://www.justice.gov/usao/ias/whitakerbio.htm
Acting appointments can’t be appointed to permanent. Whitaker’s role is meant to be temporary.
https://m.govexec.com/oversight/2017/03/supreme-court-puts-limit-who-presidents-can-appoint-temporarily-lead-agencies/136359/