Events are triggered when the graph changes, including additions and deletions.
In my understanding, all events are triggered at a point in time where the modified element is either still present in the graph (i.e. right before removal) or already present in the graph (i.e. right after insertion).
As can be seen in DropStep, AddVertexStep, AddVertexStartStep, AddEdgeStep and AddEdgeStartStep, this observation holds true. However, AddPropertyStep breaks this rule and triggers the event before the property is available in the graph.
This causes issues whenever users want to perform further actions on recently added elements, as vertices and edges are present in the graph, while properties are not.