Thanks for posting a topic!
A fundamental differentiator between a short and a shunt is whether it was intentional.
A short is a fault condition, where something happens in a circuit that provides a path to ground/neutral that bypasses all loads.
A shunt is a deliberate bypass of one or more loads, but there is still at least one load remaining elsewhere in the circuit. (I think that’s basically what you were saying in your second paragraph.)
As appliance techs, we don’t need to learn the complicated physics of electricity. We do have to accept that the behavior of electricity is described by some simple equations.
The math does show us that a shunt is NOT a parallel circuit (we demonstrate that in detail in Unit 5). This means all of the current is going through the shunt, and none to any other circuits that have loads in them that appear to be in parallel.
It is simply a truth about circuits and electricity. I’m not sure I can explain it any more clearly than what we have in Unit 5!