You are correct that each version of Membership Rewards has its own earning, partner, and bonus schedule, but a Flyertalk member's geographical location does not tell us where the card account was issued.

There is no pattern to Membership Rewards transfer promotions. Typically, there are (for example) several offers from Delta and only one from Starwood, but often there will be no offer for a few months. Some offers are organized by the partner and are never promoted by American Express (for example, Air Canada Aeroplan and some Delta offers.)