We went to an instructor who use that phrase " pitch out of the pocket ". This was to get the pitcher basically to get more arm whip by bending the elbow but nothing to do with the follow through. He said to let the arm just naturally go where it wants to after the release. In order to "pitch out of the pocket " you have to bend at the elbow if not your release with a locked elbow would be about mid thigh. I believe Doug Gillis uses this phrase and our former instructor was schooled by Gillis. [ By the way he is our former instuctor only due to logistic problems we were very pleased with the improvement ]