I have done some testing on the two new Monarco I have. I'm not sure what is correct but my findings are.
On an older Monarco I have, there is continuity between the pi and the aluminum case of the Monarco. I do not see any voltage leak on this. I think this is because the HDMI port is pressing against the case, providing a ground link.
On the two new Monarco there is no continuity between the pi and aluminum case. None of the Pi touches the case so it is isolated.
This might be normal, it is just something I have never observed before!
Should the Pi be grounded to the aluminum case?