strange spacing behavior - is it expected?

[Karol Majewski]

Hi,

Take a look at the following example:

begin------------------------

\version "2.16.2"

{
  \relative d, {
    \clef bass <d a'>4 <es g> << { a8 bes g a } \\ { d,4 es } >>
  }
}

%

{
  << \relative d, { \clef bass \oneVoice <d a'>4 <es g> \voiceOne a8 bes g a } 
\\ { s2 d,4 es, } >>
}

end------------------------

It is the same piece of music but written in two different ways. Strange thing 
is that If you compare the ouptut, you'll notice the difference. In the second 
example, third-beat column is slightly shifted, comparing to the first example. 
At first I thought it's because of spacer rest. But then I removed the second 
voice:

begin------------------------

{
  \relative d, { \clef bass <d a'>4 <es g> a8 bes g a }
}

end------------------------

and noticed that despite lack of spacer rest, spacing is the same as in the 
second example. I don't get why is this. Is this behavior expected?