[css3-values] angle unit and 0

Hi,
In css3-values [1], the text implies that "azimuth: 0" is invalid as units 
are mandatory (unlike length units (section 5)).
However, in CSS21 [2], it says
<<
Like for <length>, the unit may be omitted, if the value is zero: '0deg' 
may be written as '0'.
>>
Should css3-value say something there, either the same thing, or that it 
is deprecated.
Thanks,

[1] http://www.w3.org/TR/2011/WD-css3-values-20110906/#angles
[2] http://www.w3.org/TR/2011/REC-CSS2-20110607/aural.html#value-def-angle

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Baroula que barouleras, au tiéu toujou t'entourneras.

         ~~Yves