You have to cut the author some slack. The article appeared in a German paper, and this is a translation.
The original German for that sentence was:
Später rückten die Russen in das Gebiet ein, die Amerikaner zogen weiter nach Westen.
Maybe someone can provide an alternate translation.
We don't know if the translator was American or not, and if she had some knowledge of German military terminology.
As per Yalta agreement. Operation Keelhaul soon followed.