As i know Rotating shield frequency is about this:
If a weapon using same frequency as the shield it goes trough it. So if you rotate shield frequency The attacker cant match your shields frequency and your shield defending you better.
But i have question too. Regenerative Shields arent working this way in canon?
The regenerative shield allows a portion of the enemy fire to be diverted through the shield generator to reinforce the shield layer the amount of damage that a weapon impact does is thus greatly reduced. The effectiveness of the reinforcement depends on the shield generator design, but typically the effectiveness of a shield will be increased several fold by the addition of regenerative capacity.