Hi tadavis
This is currently the "normal" behaviour. But I have it on my todo list to improve this in following way: the opensim account still will get created, but user level will be set to -1 or so (meaning no login possible). After activating, the user will be changed for regular logins.
What currently already works is, that if you will delete a user from the backend, the opensim account will also be deleted. This is something that needs to be enabled in the settings of the plugin jOpenSimRegister.
Greetz
FoTo50