Doesn't sound right..there would have to be definitive proof that the car had exceeded the damage limits before compliancing. And it raises all sorts of issues - why was it allowed to pass through, safety issues, etc.
I highly doubt the accuracy of this.
There is a story on the forums somewhere about a bloke who didn't pass compliancing because of damage to the underbody of the car, but that was detected at compliance, not afterwards.
Accident damaged cars can still come through SEVS, all depends on the severity. If you are concerned Matty, then ask your buyer to inspect for any damage before you buy.