That's a cultural thing in the company I work for (or maybe broader in Germany, dunno), where some people think that if they start to negotiate, they might lowball candidates, and then they leave after half a year or so.

We try to hire more long term (we aim for 5+ years retention), dunno if that's related, or if there is any evidence to back this procedure.

I find it a bit weird myself, which is why as a candidate I'd like to know about it :-)