svg:viewBox issues

The spec says:

  "The svg:viewBox attribute establishes a user coordinate system inside
   the physical coordinate system of the shape specified by the position
   and size attributes. This user coordinate system is used by the
   svg:points attribute and the <draw:path> element."

First off, there is no svg:points attribute; it is named draw:points.

  "Some implementations may ignore the view box attribute. The implied
   coordinate system then has its origin at the left, top corner of the
   shape, without any scaling relative to the shape."

Obviously this has interoperability issues. Rendering points without
respect to their coordinate system is a recipe for disaster.

But beyond that, I don't see how the "implied coordinate system" is even
valid. The draw:points and svg:d attributes do not use units, and as far
as I know there is no concept of a "default unit", so the choice of
scaling factor when mapping the unitless points to the page is
completely arbitrary.

Thanks,
Chris