I am having the same issue, and this wasn't happening in previous version.
With the way this plugin is working right now every application that was using it will need refactoring...It doesn't make sense to randomly get an authentication dialog the first time you try to access the secure storage.
A flow should be presented to the user so that he understands why he is authenticating on a random ocasion.
This is also happening on CipheredLocalStoragePlugin, because internally he also access the store, and this is also something that didn't happen on previous versions.
I have never seen this behaviour in any other application, randomly asking for authenticating.