Fungibility as we have known it is based on a well supplied market. IOW you could buy as much as you wanted by switching to a different exporter if you had a falling out with your regular supplier. In a resource constrained model this is no longer the case unless you are both willing and able to outbid the other buyers and convince an exporter to ship to you instead of their already existing customers.
You are basically demanding they cut off the contracts that already exist to supply you, which is bad politics for any of the exporting majors.



