I can confirm this code works, turned in a 1-day rental at PHL tonight and the receipt shows 3100 miles. Then I turned around and drove off in rental #2... the guy just laughed and told me to keep the same car when he handed me my new paperwork. 3100 more tomorrow when i turn this one in and fly home!
For those that are worried about the budget miles posting, i've been doing these promos for awhile now and I can say if the miles show on your receipt then you are in good shape, so don't leave until they are on there. In my experience i've only had problems when trusting their website/fastbreak service to remember my info, which I stopped doing. It seems to "forget" your skymiles number or coupon number more often than not, and at most airports it only saves a few minutes because Budget is awful, fastbreak or not.
So your best bet is to make the reservation as a "regular Joe" and then pick up the car at the counter, making sure to give them your skymiles number and triple-check that the coupon and skymiles number show on the contract. Since i started doing it this way i haven't missed a single bonus.
Finally, for those that are wondering whether this is targetted, I can't say for sure because i got the email (as a PM), but I HIGHLY doubt budget's system is sophisticated enough to check with Delta whether or not you are a medallion member. Their system isn't even sophisticated enough to remember the details you put in when you reserved.