I think it's primarily a filter. Candidate filters are pretty much always silly, even common ones based on degree/grades etc. But with a lot of candidates on the market, using some filters reduces the list to a manageable amount.

Personally, as someone with a German company and a good chunk of German clients, I'd argue it _does_ help a little. Occasionally. But by and large I'm far more interested in the candidate's English proficiency.

Going to have to ask for a citation for that claim bub....