Currently nat-instance IDs are generated based on nat44 static mappings and nat64 bib entries, but nat-instance contains also address pools and nat64 prefixes (among others).
So if user does not add static mapping, nat-instance is not shown even if other features are enabled.

Adding dumps for every nat related features would fix it,
but does not scale (in terms of performance and mantainence).

One of solutions would be to add an SNAT API, that would list vrfs that have nat enabled.
Others would probably require model change (removing nat-instance concept, some of the ietf-nat model elements might be reused).