Trying to get the hang of "Polyphony with Shared Lyrics" section of the manual.

[Kevin Cole]

So. I have a piece with a few sections where there are two "voices" as
I understand things. And according to the manual, the solution, which
works fine is:

melody = {
  \relative {
    \global
    \new Voice = "melody" {
      \partial 4 bf4^\f                                             | %   0
      ef4 ef8. f16\noBeam g4 g8. af16\noBeam                        | %   1
      <<
        \mergeDifferentlyHeadedOn
        \mergeDifferentlyDottedOn
        { \voiceOne bf8 bf8\noBeam bf4 }
        \new Voice
        { \voiceTwo bf4. bf8 }
      >>
      \oneVoice
      af4 g8 af8\noBeam                                             | %   2

      \break

      bf4 c4 g4 ef4                                                 | %   3
      f2 ef4 bf4                                                    | %   4
      ,,,
}


words = \lyricmode {
  \override LyricSpace.minimum-distance = #1.5
  Let                                     | %   0
  E -- rin re -- mem -- ber the           | %   1
  days of old, Ere her                    | %   2
  faith -- less sons be --                | %   3
  trayed her; When                        | %   4
  ...
}

\score {
  <<
    \new Staff \with {midiInstrument = #"violin"} { \melody }
    \addlyrics { \words }
  >>
}

The problem is that I don't quite understand how to deal with lyric
extenders. I've looked at:

https://lilypond.org/doc/v2.18/Documentation/notation/techniques-specific-to-lyrics#polyphony-with-shared-lyrics

but the example isn't quite helping, since the way the book told me to
do the voices in the melody appears to be different from the way the
page above is doing things...