Drag and drop matching - can this be done two way?

I dont think so. At least not with the regular form view building the question. You could use a pick many and then use alot of triggers so you can drag and drop on either and state changes. 

You could change the selected state colors for each item. Matches more visually

It could be possible with a LOT of custom work.

What value are you adding by building it this way as opposed to a traditional drag and drop where you would match for example the rock on the left with the rock on the right?

Good point, I will keep it simple and drag left to right. 

Thank you!!