I can think of very few "improvising" musicians of this or any other generation or genre who would be this willing to let it get there on its own terms, not when the terms are this clear and the bar so high. Especially not in front of a bigass hall-full of paying customers.
I don't know if this is "great jazz", but it sure as hell is a great example of really improvising.
And check out Alan Dawson, just riding it along leaving that canvas totally open for anything Lee wants to play. And dig how when Dawson kinda lights him up during the fours, Lee lights him back up in return. That's a Sonny Stitt move right there, but Lee Konitz is the anti-Sonny Stitt. Yet and still, warriors gonna warrior, no matter what their battle.
And then, off he schlubs, noun as verb, motion in poetry.
Music is about music up to a point, but after that point, it's about character, period.