Well, it just gets more bizzare:
A day after I got the above from DL, I got the same (except for the name of the program) from AA!
But the timing seemed even more bizarre with AA, since their email said:
Wherever you've been eating lately, it hasn't been at AAdvantage(R) Dining restaurants.
But that's exactly where I'd been eating the previous week and a half, and in fact several of my dines had already posted, and I'd started getting "How was" emails for some of them already, when I got this "where have you been" email from AA dining offering the double miles.
Since (unlated to RN except that it works out) I have also gotten a promo from Citi for 3x miles on (among other things) dining on my AA Visa, and because the 10,000 Reasons To Party Bonus at AA is bigger than the One Bite At A Time bonus, I'm going to stick with AA miles after all, now that I've gotten the double miles (Aug 15 - Aug 31) promo from AA (as well as DL).