It is both.

"Memory safe" means that if the user is "holding it wrong", it won't cause a memory error.

In safe Rust, it is impossible to call free with the wrong address (simply by virtue of the `free` equivalent being unsafe, and with the pervasive use of smart pointers to make it practical to stay in safe land).

Similarly even if you "hold it wrong" and use a wrong comparison function in Rust's sort, you might get nonsensical results, but no memory errors.

That's precisely what safety means in this context