There is no ‘last line of defence’ with Ready to Eat foods; as they will not receive thermal treatment that kills bacteria before consumption.
Although Ready to Cook products may be more robust in general that Ready to Eat products; this does not mean that foods that are going to be cooked before consumption can be treated in a careless manner however.
Food spoilage can be sufficiently bad so that cooking instructions don’t make the food safe for consumption
Food spoilage can render the product inedible
If toxin producing bacteria produce toxins; cooking afterwards will not destroy them; making the food dangerous to eat; even if it has been cooked and tastes acceptably
In the event of re-contamination of Ready to Eat foods that can support bacterial growth; there is no competition / relatively little competition and the potential for rapid growth once the right conditions exists is more significant than it would be otherwise.