I don't think I am contradicting anything @Baluncore has said. In particular I completely agree with this:
The article at https://en.wikipedia.org/wiki/Cryptanalysis_of_the_Enigma gives some reasonable indications of why this is the case.It was well known by the cryptanalysts that the stecker plug-board did not increase security by the factor assumed by the Germans. Most cryptanalytic techniques for Enigma looked straight through, and could ignore the stecker settings for the day.
So we can see that the methods that were actually used got around the variation introduced by the plugboard. That has no bearing on whether you can ignore the plugboard if you are try to brute force a solution: as we have seen above, you can't, and we find that brute force requires testing upwards of 150 trillion settings.