[css-masking] was the position of 'mask-mode' in the 'mask' shorthand intentional?

https://drafts.fxtf.org/css-masking-1/#the-mask defines the mask
shorthand so that the mask-mode value, if present, has to come
immediately after the mask-image value.  This seems to be a bit
constraining, and it's not clear if it was even intentional, since
it seems almost like it could have been an editing error.  Maybe it
was intentional, though.

If it was intentional, perhaps it should be explained in the prose?

-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)