Yes, it was him, someone added an additional "Wilhelm" [0] and it was copied by many newspapers [1]. The Bild wrote (translation mine): "Do we have to remember this name?" [2], and some anonymous guest author on the blog claims to be responsible [2].
In 2016 the name was edited in for about 2 minutes [3], referencing a source from 2012.
However, I do not recall it being a big issue to remove that additional name again – but it was more than 10 years ago. It did, however, draw some criticism to German journalism.