Looking at those figures then surely the vic check is actually working, as only a small proportion of cat c cars put back on the road turned out to be ringers, the actual check is stopping people ringing the cheapest version of salvage cars, which is what it was meant to do. It seems most cat c cars just get broken up rather than put back on the road, the check is doing exactly what its meant to do.
A cat D is more expensive to buy in the first place so not the best to use as a ringer, with the check removed far more cat c scrappers will now be used as ringers again.