Implicit conversion and functional operators

I'm studying functional operators and can't understand why code snippets like this compile:

class Pocket
{
    int value;
public:
    Pocket(int value) :value(value) {}
    int getValue() const
    {
        return value;
    }
    operator int() const
    {
        return value;
    }
    bool operator<(const Pocket & _Right) const
    {
        return value < _Right.value;
    }
};

int main() {
    Pocket mynumbers1[] = { 3, 9, 2, -4, 4 };
    Pocket mynumbers2[] = { 3, 9, 5, 0, 4 };
    vector<Pocket> v1(mynumbers1, mynumbers1 + 5);
    vector<Pocket> v2(mynumbers2, mynumbers2 + 5);
    vector<Pocket> v3(5, 0);
    transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), minus<Pocket>());
    return 0;
}

My reasoning is that when you call the minus<Pocket> operator inside transform, the whole thing would reduce to a subtraction between two Pockets. As you can see, the class doesn't defines a proper operator-, only an operator<, which should be useless in this case, and a conversion to int, which shouldn't even be considered since both arguments are of the same type.

So what am I missing?