Are attribute dimension subscriptions possible from a single-node-type source?

Summary:

A dimension was originally established in the Universal app by Team A as a standard dimension, with a single node type, and in the Planning app by Team B as an attribute dimension, with two node types. It does not appear possible to subscribe the latter to the former, as the node converter does not allow the parent node type value to be overridden; this causes the subscription to fail, because although the parent name is correct, it does not exist on the same node type as the bottom node.

Content (please ensure you mask any confidential information):

Am I overlooking anything painfully obvious, or do I just need to convert the Universal dimension to use two node types in an appropriately-bound hierarchy set, in order to successfully subscribe the Planning attribute dimension to it? (I did check the EDM Admin Guide documentation, but didn't spot an alternative approach there.)