[css-transforms] 'transform-box' defaults in svg

Hi,
I was reviewing the 'transform-box' section in the css transforms spec,  
https://drafts.csswg.org/css-transforms/#transform-box.

The initial value of 'transform-box' is 'border-box', which is fine.  
However, the spec continues to state that:
"For SVG elements without an associated CSS layout box, the used value for  
border-box is view-box."

It seems to me that a used value of 'fill-box' in this case would lead to  
more easily understood behavior than 'view-box'. So, I'd like to know what  
the rationale behind the current choice is.

An example, http://jsfiddle.net/fs6cLt38/1/.

Cheers
/ed