That is an interesting question. I suspect that no matter what the official policy was the rules were somewhat more lax in combat.
Based on the design of the holsters and the locations of the safeties, I believe that the German belief was that the proper place for one's pistol when likely to be needed was in the hand. With the other hand available to operate the safety.
Seriously, German uniform holsters are luggage cases, compared to ours. Some even buckle closed. They are not a fast draw, or even a rapid draw item. and the safeties on the usual German pistols are not nearly as easily operated with the shooting hand as our 1911 design.
Also, the holstered pistol wasn't just something issued for duty the way ours were, they were part of the proper uniform, worn all the time. SO, I would expect they were most often carried chamber empty for daily wear, and when going into action, taken out and "made ready".
And, of course, officers do what ever they feel like, anyway...