There is a lot of significant work on Ancient Greek that came out in the 19th century. Some of it was by native Greek speakers. The challenge is that during that period, the politics of language in Greece was a source of constant debate and argument. Many times the ancient language was used as a meant to prop up one’s understanding the modern one. I picked up this book last year and only recently started reading it. It has been an extremely helpful book and has given insight into the various forces that can have an effect on grammar writing, even when you are seeking to be as objective as possible.
And it’s a stern reminder: Even academic work is not done in a vacuum and it cannot escape the political climate in which it is produced.