I wonder if the policy was changed, in part, because of the potential for being on both lists to screw up the requests. I know it's happened to me...and a few others, but is very intermittent as it's been fine for people as well. Flaky programming would be a good reason to enforce a policy like this.
Cheers.
There was always a problem in the past with a non-EXP being on both lists because the upgrade on the domestic portion could clear as X and stickers be taken when really it should clear as A. I had this happen to my GF a couple of times and we had to call to get the stickers back.