It makes sense to me.
For one thing, according to L. Ron Hubbard and what he covered in the book Science of Survival, sense of humor is connected to the emotional well being of the person. If you can spot someone on the tone scale you can predict what he or she will find funny. There is even a section in the book that helps someone locate the correct tone level (emotional state) of an entire audience in under 2 minutes. That could mean the difference between popularity and a complete flop for a stand up comic.
Then there is communication. What Seinfeld brought up in his interview was the skill he learned in communicating. It is very true that Scientology emphasizes communication as a vital part of life. If fact, Hubbard discovered that it is one of the three component parts of life, the other two being Affinity and Reality.
There are drills you can learn to improve your ability to communicate to anyone — even a dysfunctional boss or a family member. What is amazing is how effective it is– no matter what the other person is like, if you have this skill you can actually keep the stress down to a bare minimum and even improve the relationship with those impossible people you know.