Maybe you saw the text after @marcinw changed his text? I agree with you, of course I will say that most http GET actions I see are trivially idempotent -- that is to say they are idempotent because they don't change the state at all.
In fact, idempotency is irrelevant for GET, as GET requests should be safe, which trivially implies that they are idempotent. So requiring idempotency in addition to safety does nothing except making the prose harder to read.