Max M
I saw your question when it was posted but did not have time to respond. Just got back on FT and surprised no one responded.
From my experience they are correct. I have always been told you can not change the country of origin. They did it for me one time and the next agent that saw the record said this was illegal. I have been ticketing and flying out of many Asian , Europe , and South American cities for quite a few years. I normally only do refundable tickets. I did cancel a non-refundable out of the UK and had to use the residual value originating out of the UK.