It seems completely clear. He first gives unidiomatic C++ code, then next gives idiomatic Rust code, and differentiates the two based on the code snippets. It is a mistake on his part, and I do not see how it could reasonably be viewed otherwise. It is not a huge mistake, but it is still a clear mistake.

Perhaps it might help to clarify precisely what claim(s) you think are being made?

From my reading, the section (and the article in general, really) is specifically focusing on mutexes, so the observations the article makes are indeed accurate in that respect (i.e., C++'s std::mutex indeed does not have automatic unlocking; you need to use an external construct for that functionality). Now, if the article were talking about locking patterns more generally, I think your criticism would hold more weight, but I think the article is more narrowly focused than that.

For a bit of a more speculative read, I think it's not unreasonable to take the C++ code as a general demonstration of the mutex API "languages other than Rust" use rather than trying to be a more specific comparison of locking patterns in Rust and C++. Consider the preceding paragraph:

> In languages other than Rust, you typically declare a mutex separately from your data, then manually lock it before entering the critical section and unlock it afterward. Here’s how it looks in C++:

I don't think it's unreasonable to read the "it" in the final sentence as "that pattern"; i.e., "Here's what that pattern looks like when written in C++". The example code would be perfectly correct in that case - it shows a mutex declared separately from the data, and it shows that mutex being manually locked before entering the critical section and unlocked after.