I know because that's the only source that is making that claim.
I've been searching for other sources and couldn't find any.
They all claim that the legal drinking age (for beer) is 16.
There's also another website that claims 14-y-o can also drink if accompanied with an adult.
archive: https://archive.ph/fvCgp
Edit: and another one (quoting Kikepedia)
At age 14, minors can consume and possess beer and wine (undistilled spirits) in public settings with a parent or guardian. (This is called begleitetes trinken, or accompanied drinking).
At age 16, minors can consume and possess beer and wine without supervision by a parent or custodian.
At age 18, young people are considered adults. They can consume and possess beer, wine, and sparkling wine as well as distilled spirits (liquor).
(post is archived)