Yes (Rust's "unsafe" blocks serve the same purpose), and my point is you're narrowing the definition of "explicit" to exclude C or C++ by definition. And that isn't exactly a fair, in my view.

There is no doubt that C, by definition, opts out from performing bound checkings. But if bounds were always checked by default (implicitly), then you would have to opt-out explicitly, which is a safer approach, because all else being equal, in case of a programming mistake, the code ends up not being vulnerable to that specific kind of attack.