std::unordered_map<>::operator[] and its return type reference

class TestingMapClass {
public:

    TestingMapClass() : anotherStr("nothing") {}

    void Load() {
        std::unordered_map<std::string, std::string> memberMap = {
                {"name", "value"}
        };

       // Do something with the unordered map...

        anotherStr = memberMap["name"]; // The address of the local variable may escape the function
    }

private:
    std::string anotherStr;
};


int main() {

    std::string testingStr;

    {
        std::unordered_map<std::string, std::string> someMap = {
                {"one", "first"}
        };

        testingStr = someMap["one"];

    }

    std::cout << testingStr << std::endl; /// Local variable 'testingStr' may point to the memory which is out of scope

    return 0;
} 

I'm using CLion 2021.2.1 and I get these kind of 'warnings' here:

('The address of the local variable may escape the function'. 'Local variable 'testingStr' may point to the memory which is out of scope.')

From cppreference.com std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::operator[] indeed 'Returns a reference to the value that is mapped to a key equivalent to key, performing an insertion if such key does not already exist.'

But does it really matter actually? Don't anotherStr and testingStr both contain a copy of their respective unordered map's key's values (since the addresses of the strings and their respective unordered map's key's values seem to be different)?