I suspect the difference comes from the phoneticization of the name across-the-border; not different from the "Auschwitz/Oswieczim" spelling difference.
Why phoneticize a German's name into Polish for American readers?
The only reason this is done is because Poles like to pretend that Veit Stoss (and many other Germans who had accomplishments in what is now Poland) were Polish. To subscribe to such nonesense makes ones credibility and judgement very questionable.