When I saw that yesterday, one of my first thoughts was "That sucks, because now I have to find another system to practice the described chroot() breaking techniques."
I just stumbled over these slides from a chroot escape methods talk:
http://www.slideshare.net/phdays/chw00t-breaking-unices-chroot-solutions
On page 27 there's a table which method works where, and NetBSD 6.1.4
is the only one where none of the methods work at all.
Well done :)
Thomas