[css-compositing] should background-blend-mode have different list repetition rules?

http://dev.w3.org/fxtf/compositing-1/#background-blend-mode says:
  # If there are fewer items in the list than there are background
  # images, the remaining background images must use the initial
  # value. 

This is different from all the other background properties, where
http://dev.w3.org/csswg/css-backgrounds/#layering says:
  # If a property doesn't have enough comma-separated values to
  # match the number of layers, the UA must calculate its used value
  # by repeating the list of values until there are enough.

I'd prefer if the background-blend-mode matched the rules for other
background properties.  This would simplify implementation, and I
don't see the rationale for differing here.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)