I do wonder if Linus is actually opposed to Rust in the kernel, but for whatever reason thinks that he can't afford to openly ban it or do anything beyond deniably letting it be obstructed by maintainers. The Rust language project and community are political and politically savvy in ways that few other open-source infrastructure projects are - it seems conceivable that if he declared against it, this might result in personal attacks and pressure on key backers/sponsors that would endanger his position or Linux itself.