"some idiot ticked the box wrong" is reading the blog post uncritically. that's obviously the author's perspective here, but it doesn't really make sense.
he signed his name to a blank section of the form. that signature is an attestation that the blank section immediately above it was filled in truthfully. it can't be both blank and filled in truthfully. that somebody ticked off a box in that section later on is beside the point (all the other options appear to require additional information, which was also not provided, so whoever ticked off that box made a decent assumption).
it's a mistake in the same way as signing a blank check is a mistake
