Behaviour of marker coordinate system when viewBox not provided

The spec seems a little confusing and contradictory when talking about the
viewBox attribute in markers.

The contents of the
‘marker’<http://www.w3.org/TR/SVG/painting.html#MarkerElement> are
relative to a new coordinate system. Attribute
‘markerUnits’<http://www.w3.org/TR/SVG/painting.html#MarkerUnitsAttribute>
determines
an initial scale factor for transforming the graphics in the marker into
the user coordinate system for the referencing element. An additional set
of transformations might occur if there is a
‘viewBox’<http://www.w3.org/TR/SVG/coords.html#ViewBoxAttribute>
attribute,
in which case the coordinate system for the contents of the
‘marker’<http://www.w3.org/TR/SVG/painting.html#MarkerElement> will
be transformed due to the processing of attributes
‘viewBox’<http://www.w3.org/TR/SVG/coords.html#ViewBoxAttribute>
 and ‘preserveAspectRatio’<http://www.w3.org/TR/SVG/coords.html#PreserveAspectRatioAttribute>.
If there is no ‘viewBox’<http://www.w3.org/TR/SVG/coords.html#ViewBoxAttribute>
attribute,
then the assumed default value for the the
‘viewBox’<http://www.w3.org/TR/SVG/coords.html#ViewBoxAttribute>
attribute
has the origin of the viewBox coincident with the origin of the viewport
and the width/height of the viewBox the same as the width/height of the
viewport.

That last sentence is a little confusing to me and seems to contradict the
rest of the paragraph.  Does the marker coordinate system change if there
is no ViewBox, or not?

FF and Chrome apply no transformation.  So it seems they have decided it
doesn't.

Or is that sentence just intended to explain how percentage values are
calculated?

This language is in both the 1.1 and 2 specs.

Paul