Discussion:

Not everyone can sign a valid power of attorney. As a result, it is false to say (like the statement does) that "anyone" can do so.

"Valid" is a key word in the statement. If a document (like a power of attorney) is "valid" - that means it will stand up in a court.

For a  power of attorney to be valid, the person who signed it must have had "capacity" at the time they signed it. That means that, at the time of signing, the person was clear-headed enough to understand the nature and impact of the power of attorney.

Certainly an unconscious person would not have capacity. But a person with some memory loss, or who was clear-headed during parts of the day but not during others, could well have capacity - again it depends on the person's level of understanding at the time of signing.