I completely agree, but if they are able to properly (as in with predictive power for variations) build a MOSFET or anything of similar complexity they would li

I completely agree, but if they are able to properly (as in with predictive power for variations) build a MOSFET or anything of similar complexity they would likely be able to understand our concept of an electron. I believe that is very unlikely as it is very unlikely to miss atoms and then it is very likely to miss electrons. Of course I also do not think that it is provably impossible.