Inconsistency constructing std::string from C-string vs. from another std::string

Why does the std::string constructor produce different output depending only on what kind of string it is constructed from?

For example, consider the following C++ code:

#include <iostream>
#include <string>

int main() {
    char cstyle[] = "01234567";
    std::string std = "01234567";
    std::cout << std::string(cstyle, 4) << std::endl;
    std::cout << std::string(std, 4) << std::endl;
    return 0;
}

which produces the following output:

0123
4567

I would expect them both to produce 0123, or both to produce 4567, but I wouldn't expect one to produce 0123 and the other to produce 4567.

Why this inconsistency?

EDIT: This question isn't about which default constructor is called, or whether they do different things. They do different things, and different constructors are called. This question is about why they don't do the same thing. In other words, this is more of a philosophical question than a technical question.