I don't know either. But I got the SMG when I asked to PC to a cheaper AF card.
I'm neither a senior citizen (I'm 23 ) or been a LONG amex customer (Got my first amex in 2010).
I just asked if there was a cheaper AF card I could PC to and I causally mentioned Zync (already knowing it was discontinued, but it never hurts to ask) and the rep offered SMG saying the AF was only $10 more than Zync.
$35 with no rewards is a little high, but its worth it to keep an amex charge active. And the rep said I can add the standard MRE that Green gets for an extra $40 if I want in the future.
The regular green gets MR not MRe