Page 17 of “Armies of Great Britain” lists the Army Special Rules. These are
1. Bombartment
2. Artillery Support
3. A National Characteristic (page 18)
“The Western Desert”, page 102 says
If you decide to take a reinforced platoon from an
Australian, New Zealand, South African, or Indian brigade
then you may either take one national characteristic from
page 18 of the Armies of Great Britain book or take one of
the following national characteristics instead.
So clearly, the army special rules Bombartment and Artillery Support are NOT considered National Characteristics and are NOT replaced by selecting one of the two Indian National Characteristics.