I've seen this before in translation of German to English. The German word 'Maschinenpistole' is often translated as Tommy Gun, Machine Pistol and other inaccurate terms, rather than sub-machine gun.
Inaccurate. The SS used a number of different weapons, but assuming we're talking about death squads, the most common submachine gun used by the SS would probably be the MP40. The Thompson was used extensively in WWII but by Allied forces only.
Not an expert on Party weapons but I feel comfortable answering about German Army weapons.
The German was very large [20,700,000 total who served at any time] and quite good a using weapons captured during occupation of countries even giving them German designations.
It was very common to try and issue front line units with the newest or best suited weapons possible. Why you never see a STG--44 at a camp or a MP-18 on the front.
The Thompson submachine gun was never used by the German forces and not given an German designation either. That said German Soldiers would have know what they are and from some pictures showed and intrest in them [who doesn't like gangster movies?]
https://s-media-cache-ak0.pinimg.com/736x/cf/b2/bb/cfb2bbe97ca2c0bb40b531e3d4b46795.jpg
https://s-media-cache-ak0.pinimg.com/736x/fd/15/25/fd1525a8c9dbe16aa71748b58f8d1783.jpg
The major problem is SS is a very generic term. People think of SS soldier as everything from fighting in a trench in Russia, to anti partisan duties, to concentration camp guards. While true different units had different responsibilities. The SS units in charge of camps where SS-Totenkopfverbände (SS-TV) They were not combat troops. So the likely hood of them getting a hold of a Thompson were almost astronomical.
Also the most important thing to keep in mind is not everyone is a gun expert. He might of very well saw an MP 18 with a drum magazine.
