Are other MR transfer bonuses coming from the airlines? Fairly certain it's always Amex that covers it.
I'm starting to think they are both running a bonus and they just didn't clarify it well enough in their email. Also don't know that they can see that Amex is adding a bonus.
Assuming Amex covers it, it still makes sense that they miscommunicated and they are both giving it...
And even if they were running a separate bonus by their terms it shouldn't stack, which they clarified further in this email.