A documentação do Awstats diz
6.0+ for LevelForFileTypesDetection, LevelForSearchEnginesDetection, LevelForKeywordsDetection, LevelForWormsDetection
# Following values allows you to define accuracy of AWStats entities (robots,
# browsers, os, referers, file types) detection.
# It might be a good idea for large web sites or ISP that provides AWStats to
# high number of customers, to set this parameter to 1 (or 0), instead of 2.
# Possible values:
# 0 = No detection,
# 1 = Medium/Standard detection
# 2 = Full detection
# Change : Effective for new updates only
# Default: 2 (0 for LevelForWormsDetection)
Então, parece que LevelForRobotsDetection=0
fará o que você quer, e deve ser bastante fácil testar também.