I remember some discussion about that a while back on HN. The TL;DR is a) he does say that and b) he would say that, since lzip is effectively a competitor to xz.
That said, I've been using pixz (which is compatible with xz but can do parallel decompression and a few other things) for many years on many dozens of terabytes of compressed data and have never had any problems.
That said, I've been using pixz (which is compatible with xz but can do parallel decompression and a few other things) for many years on many dozens of terabytes of compressed data and have never had any problems.