Interfaces data unavailable in nb_inventory compose?

[bluikko]

I am trying to compose host variables from interfaces data in nb_inventory but it does not seem to work.

Something like:

interfaces: true
compose:
  test_var: interfaces

The test_var is not seen in the host variables: so it looks like the interfaces variable is not available in compose.
The above is just a test, usually the composed variable would be much more complex but it would start with interfaces | ...something.

Am I doing something wrong, or even with interfaces: true the interfaces data is not available to compose?

If it is not available then why? Can it be added?

I would like to avoid the constructed plugin if possible.