> If I teach English as a foreign language, am familiar with the kind of mistakes non native speakers make when writing in English, and can easily identify texts written by non native speakers - that’s not confirmation bias.

And if you immersed yourself in the writings of non-native English speakers for a significant amount of time, then a paper written by a native English speaker was presented without you knowing who the author was, would you look for the same kind of mistakes in it that you have been finding?