My take on it is that the EM 2 was really copied from early WW2 era technology it was nothing new, by the time it was briefly issued it was obsolete in many ways, especially it's laborious construction bored and milled from solid, which was long obsolete in terms of German technology. The EM 1 ( Thorpe ) was more advanced than the 2 by copying later war technology in the Mauser roller locking system but was ridiculously over complicated, if they had simplified it maybe it could have been a better option than the EM2, certainly cheaper to manufacture. But the Germans were already way ahead of the EM2 even in 1940 with such weapons as the FG42 and this stamped Knorr Bremse prototype which makes the EM2 look from the stone age.
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Both the US trailed and rejected a bullpup Garand and the Soviets a bullpup AK style design ( koborov ) so even the bullpub format of the EM2 was not unique.