I don't understand why some people would think that but you're right because there are some people who think others aren't native, when they say a grammatically unnatural sentence or an unnaturally grammatical sentence. I don't understand how a grammatical sentence can be unnatural. I think people don't have to be native to say things right but I think people should be understood. I don't know if people are going to think whether I'm native or not because I learned two languages around the same time when I was younger. I still think "I told that to you" is correct and I heard people say "I said that... to you" is correct. Is it?