Earlier quoted context omitted.
I enjoy the Wambaugh I’ve read, but I had some issues with this article. Version_five is right about Martin Beck. (I wouldn’t count Maigret or Chandler as “police procedurals”.) Also on the list and predating Wambaugh: Ed McBain’s “87th Precinct” novels. First one published in 1956, last one in 2005.
Do Sherlock Holmes stories not count?
While the more abstract elements of puzzle-cracking are brilliantly elaborated within a legal mystery framing in the Sherlock universe, I would say police procedures themselves are barely to be seen except where he benevolently tolerates or accedes to them at the request of others.
Investigative rigor and procedure are common to both forms, but the police procedural itself has a considerably wider remit I think that even the classic lone wolf cop fits into in a way that types like Holmes and modern successors like Jack Reacher do not.