Any of the skeptics out there should go to the following web site:
http://iwk.mdw.ac.at/index_e.htm
Click on research then on mouthpiece forms. You will then get a small dabbling of how very small changes in shape can change the intonation and playing characteristics of the mouthpiece. It is possible to correct for many of the "unnatural" things that we do when playing trumpet. Tension is one of them. Great players get the job done. Some of us will make an effort to find hardware that makes our job just a little easier. The differences are not subjective (ever heard of the "pivot" system? Why was it even necessary?). Ever had to use alternate fingerings to get your C trumpet in tune? Yes, you can get the job done with conventional equipment. There are technical shortcomings and manufacturers out there trying to solve them. Playing tense is not good AND very common. Mr. DM is one of those few that are making progress getting clients to relax!