I don't think that the people who do lead pipe buzz are specifically thinking about widening the pitch center in their playing. But I do believe that it helps. I also think, perhaps, that this is the benefit which they enjoy without actually knowing about it. Yes, I've already mentioned lip bends above. But there are different ways to do lip bends.
Some people only bend the note a half step flat.
This, as I mentioned above, aids us in finding the center of the pitch for that note. But other people practice bends of intervals larger than half steps. The notes are rejected and it's our goal to make them sound just as good as if they were fingered correctly. Lip Buzz Lip buzz is not directly related to widening the pitch center, but I feel that learning how to control a free buzz can really help teach us how to control the embouchure. After all, if you think about it, all of these pitch center widening exercises deal with buzzing one pitch while the trumpet is set to resonate to another.