These tribunals enjoy a position of independent operation. It was judged, as I understand it, that part of that reality was that the department—which, remember, has its decisions being reviewed by that tribunal—was not privy to the caseload and the rate of resolution of the cases. After the fact, the caseload was growing during that period between the announcement of the new tribunal and when the Social Security Tribunal began.
On April 21st, 2016. See this statement in context.