Jacob,

"Einstein himself was not convinced in 1936. In a paper with Nathan Rosen he came to
the conclusion, that gravitational waves do not exist!"

I would say he was right. All the changes afterwards were NOT confirmed with Rosen, Einstein has been ignored in his later years and his work accelerated away from him by known pions of relativity theory and quantum mechanics.

And in the paper you provided you can see they 'tricked' the gravitational waves back into theoretical existence. I do not like 'tricks'. It is science bias, very dangerous.

Regards,
Daniel