How is it the default in Rust? Like C++, the Rust stdlib gives you both options (std::path::Path::metadata). It boils down to calling stat vs fstat (on posix systems), and it's up to the programmer to make the right choice.
It's about nudging the developer to do the right thing out of the box even if they aren't really aware of all the intricacies. Ergonomic design like this will become a big deal in the future: even if you have very little idea of what you are doing the program actually will be reliable and do the right thing, provided you did not stray too far from the path the language (and the library) nudges you towards.
I agree that that is generally what Rust and the Rust stdlib try to do, but I don't think it holds in this case.
Iterating through a directory generally yields a Path or a DirEntry, both of which have a metadata method readily available, and neither will nudge you to open the file first and then calling metadata on the open file.
