This is absolutely correct! Took me two times (and two broken safeties) to realize that using the decocker on an empty chamber will cost you $$.Oh, also-
The folks at Walther forums advise against use of the decocker if possible as broken hammers and safeties are a thing. If you must use it, its best to lower the hammer slowly with the other hand. Same thing goes for the P38/P1 pistols.