Present imperative in Koine

Apart from the present imperatives with a general sense and the present imperatives derived from non-transformative verbs, the present imperative in the Koine seems to be used only when both the speaker and the hearer have fully been informed of the situation on account of which the speaker decides that the action ordered has to be performed.—The Greek Imperative, page 85

<idle musing>
Hmmm...this one is testable. What do you think? Is it true in the NT? Could this be why Paul starts out with the theological justification of his imperatives? And sometimes starts out with aorist ones, as well?

Makes sense. But what of 3rd person imperatives? Is that a more polite version of a 2nd person imperative? That's what I think, anyway...
</idle musing>