auto_complete_result field rather than method?

I just noticed that the auto_complete_result method in the
auto_complete plugin calls the field (as opposed to the method) to
generate the result list.

Here's what it is:

  def auto_complete_result(entries, field, phrase = nil)
    return unless entries
    items = entries.map { |entry| content_tag("li", phrase ?
highlight(entry[field], phrase) : h(entry[field)) }
    content_tag("ul", items.uniq)
  end

I've changed it to (and what I think it should to be) :

  def auto_complete_result(entries, method, phrase = nil)
    return unless entries
    items = entries.map { |entry| content_tag("li", phrase ?
highlight(entry.send(method), phrase) : h(entry.send(method))) }
    content_tag("ul", items.uniq)
  end

What is the rationale for using the field rather than the method?