I've experienced the "hatch rattle", and I really don't think it is the hatch.
My rear hatch is very tightly coupled to the body when closed. I can get
no budge from it, no matter how hard I lift against it. So, I really can't
imagine a bit of wind coming in the window would make it rattle.

However, I have heard something about some small vents at the back
of the car, which I've read have their outlet under the taillights. I understand these are vane'd, which vanes open to release pressure when
the hatch is being closed (when all other openings are closed) as a result
of the increase in volumetric pressure.

So, I'm wondering if what I'm hearing as a "rattle" is really the fast
opening and closing of these vanes when the wind blows into the window
with extra force. I.e. window down at 75 does not produce the effect.
But, if a crosswind blows into the open window while driving at 75 I
hear the rattle. Sudden increases in pressure, not bouncing on road
bumps is what seems to produce the noise. At least, in my case.

Coyote