In Generation's defense, it's safe to assume the Duras sisters could have obtained more than just the Enterprise's shield frequency in the diagnostics Geordi transmitted, like weapon modulations, to better defend against the Enterprise's counter-assult.
I never thought of that before, but it is a excellent idea.
If the Dura sisters knew not just the Enterprise's shield freq's, but also the phaser modulations at any given moment they could adjust their
BOP's shield freq's to provide the most protection possible.
You be smart, please father my young.