Switch node input's cost

Recently i made a simple ambient occlusion switching graph, so that i can choose whether i want to use HBAO or RTAO with a simple press of a button instead reconnecting nodes. 
What is not clear to me is how the final cost of a switching node is calculated.

For the switching to work do substance need both HBAO and RTAO to be calculated? Because if i open the graph and recalculate it then it shows both the HBAO and RTAO timings, thus you could deduce that it actually needs both to be ready when needed. *1st attachment shows this

But if i would instantiate this graph into another and use it that way, choose HBAO for the ambient occlusion, then in that instantiated form the timings indicate that only HBAO got calculated in the end. *2nd attachment shows this

How does Substance Designer handle computation costs for nodes when using a switch node to toggle between computation paths? Is computation only performed for the active path, bypassing inactive paths?
Or does it only calculate the inactive paths when it needs to show for example the thumbnail of nodes?