I doubt the policy has changed, just the technical implementation.

Do a test dine and see what happens. Do you get miles in all programs, or just one of the programs, or no programs at all? If just one of the programs, is it the last one you registered that card with, or a different one? If just one of the programs, if you go back and look at the credit cards registered with each program, does it at that point still show the same card registered with multiple programs?

Once they didn't allow you to register a card with another program without first manually removing it from the previous one. You got an error message.

Then IIRC they changed it so that you could register a card in as many programs as you wanted, and it simply removed that card from the previous one when you registered it in an additional one. You got no error message, but if you went back and checked the original program that card was no longer registered there.

Did you go back and verify that it still shows the same card registered in all those programs? If so, the latter method of lockout may have disappeared.

But all that may be simply because their per-dine process can now weed that out. It may be smart enough to know to only issue a dine to one program (whichever program it feels like, among the list you've registered the card for), in which case there's no need to lock out at registration time (tho it might be nice to alert the user who's doing this by mistake!).