It's different then because…say I'm the nurse at a health centre and someone I know walks in. I've seen them and I know their name. If it matches up with their file of providing services and they happen to live in the poll that I live in, then that is a requirement that is met.
I think what you'll see in these situations is that each part of the system, whether it's the vouching or the letter of attestation, has a bit of a different scenario for the individual, and the current suite of options provides the most ability for everyone to vote.