gradient edge case

All,

Currently the canvas spec specifies the following:

If x0 = x1 and y0 = y1, then the linear gradient must paint nothing.

and

If x0 = x1 and y0 = y1 and r0 = r1, then the radial gradient must paint
nothing

Why is this? It seems that the gradient should just be a line or circle
that has the first colorstop's on the left/inside and the last colorstop's
color on the right/outside.

Rik