Your quote (I didn't check the url link to delta.dumb) says travel originating in the US...so RT tickets US-EU-US or US-Asia-US, for example, should be included. I've always been reassured on the phone (NW PE, DL PM, and DL DM lines) that I have until midnight the next day to cancel international M+upgrade tickets with no penalty, although I can't recall when I last tried to cancel one.