Within TTGL pilots are basically godmode
So is Yuki.
I am no haruhi expert just looked at her wiki but didn't it say when Haruhi asked her to use some magic attack she goes "Umm no..."
The idea is to not let Haruhi catch on that Yuki's anything special.
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~Tommeri Uranius Bombaldi the Fourth, esq.
(aka not Krakenprophet)