Full steps:

Go to Dashboard / Site administration / Users / Privacy and policies / Plugin privacy registry

Open 'Enrolment method' and find 'Cohort members to group'

What I expected:

No icons except 'Additional', whose icon text is "An additional plugin installed on this site."

What actually happens:

Both 'Additional' and 'Userlist provider missing' appear. The icon test for the latter is "This plugin has the base provider but should also implement the userlist provider for full support of privacy functionality."