Yes, this is for 'SnapCenter' Plug-in. I am not the end customer, this is for one of my customer. Is it possible for your to share the compatibility screenshot? Cause I was not able to login to the matrix link.
Also should this plugin be unregistered before upgrading vCenter Server and registered back after upgrading?
Have attached the screenshot, but I would like to suggest that you should get the login sorted as this will help you understand the components mix and it's interoperability and also access to NetApp KB and other resources.
Ideally, the plug-in should get refreshed ( as the vCenter Host/fqdn/IP is same, its just an upgrade). But, it incase there is any issue refer this article to 'UnregisterExtension'.