Yes it does make sense what you want. But it will mean lying to the vet as to when your dog actually started having the fits.

Any pet insurance company will only let you make a claim once 14 days have elapsed from date policy starts and anything that crops up in that 14 day period isn't covered.

So is it fair to leave your dog that long before you seek treatment? I know I certainly wouldn't! Your dog could have a fit and die... whilst you deny it treatment.