Double 'shapes' in shape files

[dunn <dnaughton dunnamin com>]

If this is more of an svg question and not something particular to Dia, 
just let me know please!

All through the sample files, the shapes have xml like this, with two 
calls to ellipses, rectangles, circles:

<svg:svg>
  <svg:ellipse style="fill: default" cx="5" cy="5" rx="7" ry="7"/>
  <svg:ellipse style="fill: none; fill-opacity:0; stroke-width: 0.1; 
stroke: #000000" cx="5" cy="5" rx="7" ry="7"/>
</svg:svg>

...but I get the same effect with just one call and a thicker 
stroke-width like this:

<svg:svg>
  <svg:ellipse style="fill: default; stroke-width:1" cx="5" cy="5" 
rx="7" ry="7"/>
</svg>

I really don't even see how the sample files get a thick line from this, 
since stroke-width:0.1 gives a hairline and the radii are the same in 
both the calls.

Is there a reason to make shapes the first way as opposed to the second?

Thanks,
   -- Dunn