Disable registration not remove all data

It works this way on purpose so if you re-activate, you get your old settings back. There is nothing wrong with have settings data stick around. That said, adding an option so it does go away isn't a bad idea either. Changing to Feature Request.

Sorry, I didn't elaborate, but this is a problem in views that use the "node registration settings" relationship and the status value to know if a registration is active or not.

When a deactivated registration (without a type) is created, there is no data in the registration_settings_field_data table; the relationship will have no value (it is considered inactive).
If an activated registration is created, there will be a status value (active or inactive).

But if a registration that was previously activated is deactivated, the status information persists and indicates an incorrect status.
A new deactivated registration and an old one that is deactivated do not have the same state.

There may be a problem in the view's "node registration settings" relationship...
If a registration is disabled, the relationship shouldn't return the settings information. Yet it does.