question

Hope we are talking here about single phase things and not split phase things, right?

Any power source will have (at least) 2 wires/terminals. The idea is that somehow both those wires to touch the human body in order for the circuit to close and the current to flow.

A floating power source (with neither terminal connected to earth) will have 0V potential between any of the terminals and earth. But it will have full voltage between its terminals, because between its terminals the power is generated.

When you ground (verb) any of its terminals, that terminal will be brought to the same potential as the grounding point and that point can be considered as a voltage reference.

In your circled image, both the leg and the arm have the same potential (earth and neutral, because they are connected together) and therefore no current will flow.

Keeping this in mind, take a look at the pictures and where you will see that both Phase and Neutral touch, through any means, the human body, that is a danger situation.

I am saying "any means", because the Earth (the planet / the big blue marble we are sitting on / etc) can be considered a continuous wire between any two physical grounding/earthing points on this planet.