How much "buffer" or margin of error is in food safety guidelines?
A lot of the "time out of fridge" and similar guidelines must have quite a lot of buffer in a cool domestic kitchen compared to a hot commercial kitchen for which they're written. This is because the temperature is the food is what matters and that will change much more slowly is the ambient temperature is closer to fridge temperature. There's less margin for error in the temperature something must reach to be safe, and even less in things like hand washing and not preparing salad with the same tools as raw chicken.A lot of the commercial rules are about proving it's safe as well, even if shifts change. 

Much of the advice given here quotes US FDA rules, which go further than many other countries. Recently we had a discussion about Australian guidelines on cooling hot food, which allowed considerably longer. The US still has a higher incidence of food poisoning and especially botulism than many other developed countries, even though it had some of the strictest rules.