I absolutely cannot believe it’s not as easy as selecting the prototype wire and then grabbing the origin circle and moving it to another element, just like you can do with the destination (arrowhead).

Please give me a use case where it’s more common for users to want to create another interaction of the same element going to a different destination than it is for a user to rewire an origin point.

The only use case that springs to mind is when wiring up internal component variations, but I always do that via the Interactions palette and select the variation from the pull-down menu rather than manually drag the connections. 

Maybe I’m not the average user here, but it seems like Figma could have easily reimagined their wiring UI to facilitate changing the origin. Like make that the default behaviour and then add Opt/Alt to create a new wire from the same origin.