The Supreme Court hires people for many cases. They are not experts in many things. They hire them as advisers and they often hire them to actually figure out technical issues. For example, I recall a border dispute between Maryland and Virginia about 10 or 20 years ago. The Supreme Court hired a team to figure it out and they made a recommendation and the Court went with the recommendation.
At this point it is not clear in what capacity Wilkerson has been hired for. None of the articles or twitter feeds I've read mention the hire is a special master...
Did the judge hire a lawyer in order to write all his legal decisions involving Flynn? Of course not.