Baborak bunches his chin up as he ascends for the last note of Don Juan.
Interesting to watch! And what a grand moment in classical music to savor. Does it get any better than this?
Some of you may have already come across Froydis' article about "nevers": http://www.hornsociety.org/en/
With examples like these, it's hard to see how some believe bunching the chin or puffing the cheeks is "bad" or even "damaging" to the embouchure.