[css3-images] new side-or-corner keywords?

http://dev.w3.org/csswg/css3-images/#linear-gradients

I've never heard of start, end, before, or after used with linear gradients until now.  Nor do I have any clue what they are supposed to mean.

Did I oversleep a month or something?

Why are we adding arbitrary new capabilities now?  I thought we had an ED that we could move forward yesterday; now I have no idea.