Play nice children.
There can be no current flow through a domestic distribution circuit from a socket outlet unless there is a load connected, and, unless there is something plugged in, then there is no load connected, ergo, no current flow.
(From a real registered professional engineer)
Your current advisor is either misunderstanding the scenario, or, there is a mix up in questions somewhere along the lines.
The fact is that regardless of whether the switch on the socket outlet in the picture you posted earlier to which I quoted & replied, there can be no current flow as there is no current path between the outlet pins of the socket.
In fact, going from memory looking at that MK socket, it is double pole switched, and, thus isolates both live conductors in the socket when switched off, when switched on, it will allow current to flow, when a load is plugged in.
IF, the switch shorted out the supply as in the hand drawn diagrams you posted then the circuit protective device would operate every time the switch was closed with no plug inserted.
Also, the "box of tricks" drawn into the supply line does not exist in a distribution circuit.
If one is talking about connected appliances such as a phone charger, or TV, laptop power supply etc, then that is a different story.
These contain switched mode power supplies, passive and perhaps active components, which have parasitic losses, such devices do not exist within the electrical installation between your socket outlet and your electricity meter, unless they are deliberately introduced by wiring, or fitting a BS1363 socket with built in USB outlets for example.
However, the socket in your picture is simply a BS1363 socket outlet, it is a totally inert device, with no transistors, or other passive/active devices, thus it cannot "consume" power, and thus, there is no leakage, unless there is a dangerous fault within the installation, and if that fault were at the socket, it would manifest itself quite quickly.
So, unfortunately, your friend/other contact, is either misunderstanding the scenario for some reason, or, really does not understand the distribution side of electrical installations in premises.
"His" diagrams to not reflect how a distribution circuit to a BS1363 socket outlet is in real life.
His ac source, would be the socket outlet in these diagrams, the box of tricks would be the load, washing machine tumble dryer, phone charger supply, etc, and the switch on the socket would be up stream of that, the way that has been drawn is neutral switched, which is only allowed within appliances and devices built to a product standard.