I just noticed that the SEP has a new entry on the Xunzi, penned by Paul Goldin (published earlier this month). (Look forward to reading it, Paul!) The older entry, penned by Dan Robins, is linked to at the top of the current one. I don’t know what goes behind the editorial decisions to replace existing entries with newer ones by different authors, but I think it’s great that readers will have more than one perspective to look at when turning to the SEP, which has been a go-to site for me when I want to read up on an area of philosophy foreign to me.
I was told that they update their entries regularly, and Dan didn’t want to revise his. I don’t know more than that.
I believe all former entries are saved on their archive site.