It's missing the point of these changes to suggest that the current version is good because the error has a just-so explanation. The same code without the MutexGuard is conceptually the same, and there a mutable reference is dereferenced twice without an error. Should the programmer need to know that they themselves need to manually write the mutable-reference coercion that the compiler would normally do to unlock the same expressivity? Is this good and intuitive language design?

>Is there an example that really benefits from these features?

That question would be easier to answer if you would spell out what you don't find compelling about the article's example, beyond the fact that you can identify a reason for the error to occur.