I am wondering where the information comes from that the "author may be a fine teacher in his own language". Moreover, if we grant the argument of "a native English speaker", then it follows that each one has to write only in his mother language. Just imagine all the doctoral and post-doctoral works in the world to be rewritten by "native English speakers".
Nikolaos Bakalis, author of the
Handbook of Greek Philosophy: From Thales to the Stoics Analysis and Fragments