Many customers use GT-Subset and Data maker to create subset and cloned Data Generators using the Data Creation Assistant in Data maker. Having the same product suite saving relationships in different repository tables doesn't make much sense. Given the Portal as the direction, there should be bi-directional capability to use the relationships found in the portal with the Data maker/Gt-Subset to work with the data creation assistant.
Why does the TDM Portal store Subset relationships in different tables from GTdatamaker/GTSubset?
TDM Suite of Products:
A decision was made not to have a bi-directional relationship between the data model in GTdatamaker and portal due to differences in how the data is stored in the repository. As a result, this is a conscientious and deliberate design. To change this, you would have to go to the communities to enter in an Enhancement request, get it voted on, and if approved then wait since it is a Framework Design Change.