In what context? Given this category is seems you are talking about in a binding but it’s not absolutely clear.
My understanding, at least for now, Bindings are not allowed access to the PersistenceService. And if you are creating a binding that depends upon that, consider the fact that it is not required to have any persistence service at all. What does your binding do in that case?
Technically anything can be accessed from a binding. But the OH architecture is built around layers of abstraction and interfaces. Just because it’s technically feasible for a binding to access Items and Persistence does not mean that any binding that does so would be accepted by the OH project.
So if you’ve no plan to release this binding as an official add-on to the openHAB project, you can do what ever you want. But if you do have such plans, your binding must follow the restrictions and policies of the openHAB project which dictate that Items and Persistence are not to be accessed from add-ons.
By also changing the startlevel to 79 (before bindings), it allows the persistence service to be called from bindings to persist previous (ie offline sensor time series being reported when sensor is offline) or future time series data such as electricity prices or weather forecasts.