Else, Someone on Nostr: Yes, I think you understand it all correctly. The difference is, in Nixpkgs we only ...

Yes, I think you understand it all correctly. The difference is, in Nixpkgs we only allow a very simple type of constraints, such that you do end up with a static dag with a finite set of inputs that you can tweak to recompute and drastically change the shape of the graph, and "resolution" is literally just graph traversal, a direct computation. What people normally mean by "version solving" is you only describe the inequalities, ...