If that's all that he did, then I'd have no concerns. He likes to talk down other up-coming programming languages, too.
But they've got something his language doesn't.
Did he say something that offended you? He shares his opinions to people who ask about it. Often his opinions are shared on his livestream - which is an environment he ultimately owns.
I’m a bit shocked at your attitude with this. Your conviction is unnerving. The existence of jai doesn’t prevent the existence of Rust or other languages.
However I don't think there is any need to suggest he's a "fraud", the language is "fantasy" or faked for the stream. I also don't think that there is any need for him to release the compiler.
Have you considered that Jai is just a hobby project? Many programmers choose writing a programming language as a hobby project so why shouldn't he? Releasing a compiler to the public and having everyone demand that he also maintains it for every corner case they have is a lot less fun than just working on it for your own scope and showing it off/discussing it in your stream.