This question has been asked before, here is another old post:
https://scn.sap.com/thread/2141209
We use a user exit to check for restricted countries. I'm not sure about the Embargo field, but if I knew about every field in SAP that doesn't work or works not as expected, I'd probably be very, very rich. 
You could also send a message to SAP that the field is not working, let them really work for their maintenance fees.