Hi,
we created a managed package where we also deliver picklist values to a global picklist which is included in the package.
After we deployed this package on a subscriber org and on the subscriber org, we added new picklist values and disabled some values which came with the package in the mentioned global picklist.
On upgrading the manage package, all changes made on the subscribe for this global picklist is gone.

If I understand this description correctly: https://developer.salesforce.com/docs/atlas.en-us.packagingGuide.meta/packagingGuide/packaging_component_behavior.htm

Picklist Values
Subscribers can rename or delete picklist field values. Carefully consider this when explicitly referencing a picklist field value in Apex.
Picklist field values can be added or deleted in the developer’s org. Upon upgrade, no new values are installed. Values deleted by the developer are still available in the subscriber’s org until the subscriber deletes them.

So this should not happen, right ?