This old thing was a college bass from 1954 until last year, and the endpin survived with only the one chip you see in the photo. I think it's neat. I've seen at least one modern collet-type endpin, although it's metal. There'a a photo of it in this article.
http://www.hamstringsmusic.com/Doubl...%20article.pdf
I should add that this old one does not slip with only minimal tightening. The collet just seems like a more elegant design than a bolt jamming your endpin in place. You could do the same thing with a cam clamp instead of a threaded collar.