Why doesn't Ideographic (ID) in UAX#14 have half-width katakana?

[Makoto Kato]

Hi.

http://www.unicode.org/reports/tr14/proposed.html#ID defines Ideographic
(ID).  Although full-width katakana is included in ID, half-width
katakana (U+FF66 and U+FF71-U+FF9D) isn't.  Why?

Also, Conditional Japanese Starter (CJ,
http://www.unicode.org/reports/tr14/proposed.html#CJ) considers
half-width variants such as half-width katakana letter small a.


-- Makoto