I understand your question. A "certified" copy is simply a copy. In
practice, it depends upon the requirements of the accepting person (eg a
bank) about what they want. They can, and do, simply copy the original
themselves if it can be conveniently provided, and it's all done and
dusted, as you say.
Where that can't be done conveniently, a copy is provided. Typically,
it's called a "certified" copy ie someone writes or types on the copy
that they "certify" that it's a true copy of the original. There are
millions of these certified copies created, but they have no particular
legal status. The person who does the certifying is typically specified
by the accepting person. In principle, the document could be certified
by anyone at all. To give it more "authority", however, the person
doing the certifying might be a solicitor, or someone who has a really
impressive-looking stamp. That, of course, is mythology.
With POA, it's exactly the same, although section 3 is there.
But, in all cases, the requirements of the accepting person are what
counts, because accepting people are usually well-aware of the
possibility of fraudulent documents being manufactured, and they are
risk-averse to that kind of thing.