Stalag IV A Mobilised 26Aug39 at Hoyerswerda, 10Sept39 Elsterhorst, 1Feb41 Hohnstein Sachs. Schweiz.
It was authorised under the Geneva Convention to be employed outside the camps. That's where your secondary reference came from. Same thing happened in UK and Canada with German and Italian prisoners.
Wehrkreis IV (Military District) HQ Dresden had stalags A to G. oflags (Officers camps) A to D including the famous/infamous Oflag IV C Colditz Castle.