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.