Not really. The stock lug was kept just to simplify production. Since 1914 all P.08 pistols have it.

Some time just before ww1 they began adding that "stock lug" to all the frames, if for no other reason than it gave the builder a neat way to hold the gun during assembly/fitting. Only several models actually were intended to use a shoulder stock during firing, the Artillery, Navy and Carbines, as they were issued or sold with the stocks. Fast forward to our Gun Control act of 1934, when it became illegal to put a shoulder stock on a pistol with a barrel shorter than 16.5", however those 3 models were eventually excluded so long as the correct stock was mated to the pistol. So depending on how your pistol frame was originally issued (what model) it may or may not have been originally intended for use with the stock.
That extractor being raised does indicate that something is wrong, broken, or very dirty, so show it to someone who knows Lugers. Where abouts are you located?
dju