A belief such as 'I am all-knowing' is a perfection in God because it is true of God, but the same belief in a finite creature who is not all-knowing would not be good.
The resemblance requirement identifies a necessary condition for being good, but it does not yet give us a sufficient condition. This is because there are ways in which finite creatures might resemble God that would not be suitable to the type of creature they are. For example, if God were all-knowing, then the belief, “I am all-knowing,” would be a suitable belief for God to have. In God, such a belief—because true—would be part of God’s perfection. However, as neither you nor I are all-knowing