Comment 4 for bug 168428

The source XML file says exactly this:

<sect1>
<title>Drop shadows</title>
<para>
Inkscape supports the Gaussian blur SVG filter, so you can easily create blurred drop
shadows for objects. Select an object, duplicate it by <keycap>Ctrl+D</keycap>, press
<keycap>PgDown</keycap> to put it beneath original object, place it a little to the right
and lower than original object. Now open Fill And Stroke dialog and change Blur value to,
say, 5.0. That's it!
</para>
</sect1>

As you seem I fixed it on my side :)

So it's just SVG and webpage are not up to date