That is good advice, but I'd like to clarify that I meant variation over diversity. Eating the same 15 things every week is better than eating the same 5 things, no doubt. But changing it up over the week, month, is even better because is diminishes the chances you're getting too much of something that might be bad in great quantities and works with the adaptability of the body.
Fasting seems to be good for you, for example, because it stimulates the body to consume malformed proteins. Changing intake up from one day to the next also should help the diversity of the gut biome and the activation of several metabolic pathways without 'overheating' any of them.