Collider2D with Joint2D to world can't collide to another Collider2D w/o Rigidbody2D

I have 2 Collider2Ds A B, all Box for example.
A has a Rigidbody, B not. Then, when A fall, it can hit B.

Now, A adds a Joint2D(any kind, e.g. HingeJoint2D), connected to null(means, the world space), set prop parameters, so it can rotate like a pendulum.
But, A cannot collide with B any more!

Unless:
1. Joint2D.collideConnected set to TRUE, though the Joint2D is not connected to B;
2. B add a Rigidbody2D component, but it is intended to be static, so isKinect is then always be true.

There are other issues (or bugs) in Physics2D, like max velocity is sealed to be 100. Maybe something more need to do between Unity3D and Box2D.
Please Fix them Or Document them. Thank you!