No, the rules haven't changed, but oftentimes there is confusion between Membership numbers and Contract numbers. A Contract is for a specific number of points at a specific resort in a specific UY, and when that contract is re-sold it retains those characteristics (although DVC assigns a new number to that Contract). A Membership can contain multiple contracts from multiple resorts, but all the contracts in a single Membership must have the same UY and the exact same owners (exactly the same names, listed and spelled the same way - for instance, if one contract is under wife's maiden name and the other is in her married name, that would put them into two separate Memberships).
So maybe she was thinking of Contract numbers, which would be different for each of these two contracts, as opposed to your Membership number, under which both Contracts would be found as long as both Contracts have exactly the same owners and same UY.