I've never heard of a date that goes along with a code being blown. I'd pin it on your accident, the field appraiser(the guy from the insurance co that looks at the car) will determine if its related or not. Field appraisers don't check the engine code, they let the shop do that and the shop and field appraiser agree if the damage is related. Chances are your shop can make it look like its related, they want the extra money from the insurance co.

P.S.-I work in a claim center and all sorts of sketchy stuff goes down all the time. I see files all the time of people getting into accidents only to modify their car and get a new body kit, or a new paint job. the insurance company looks the other way most of the time. in your case the worst that will happen is they won't fix your code problem. they won't accuse you of fraud cause you're playing dumb and didn't know.(make sure you play dumb)