I’ve found the original, untranslated German quote:
In einer anderen Publikation sagt er: Wenn es im Universum noch irgendwo intelligente Lebewesen gibt, dann kennen sie vielleicht Schach, höchstwahrscheinlich jedoch Go.
“Höchstwahrscheinlich” actually means something more like ‘most likely’.
I find it easier to believe that the English came from the German than vice versa. My hunch would be that an American saw the translation attributed to ‘E. Lasker’ and jumped to the conclusion that that referred to the (more famous in the US go world?) Edward. Of course, it could have been the other way round …