Perfect logic:
NetGraph[{1, 1, 1}, {1 -> 2 -> 3}]
But this does not make sense:
Graph[{1, 1, 1}, {1 -> 2 -> 3}]
How can Rule behave differently when called by different functions?
Rule
Next time, if you cross-post, please links the posts together.
https://mathematica.stackexchange.com/questions/187113/why-graph-does-not-recognize-chains-of-vertexes-like-netgraph
To sum up the answers there, your notation considers 2->3 to be a vertex, connected to vertex 1. This notation cannot be made consistent without restrictions on what expressions can be vertices. NetGraph restricts vertices to integers and strings, so it can disambiguate such notation.
2->3
1
NetGraph
