current_user_can(‘Administrator’) does not return true in multisite if user is Administrator but NOT Super Admin

I would agree that current_user_can(‘Administrator’) should return true for the user. However, current_user_can is primarily intended to check for capabilities, which is generally a more robust check to be making.

I’d suggest something like this (untested):

if ( current_user_can( 'activate_plugins' ) && ! current_user_can( 'update_core' ) ) {
//...
}

So this is checking if the current user can activate plugins but cannot update core. This should return true for Administrators whilst returning false for Network Admins – as on multisite update_core is reserved for Network Admins.