It's not really. Most traditional religions have fasting practices and pretty much all our ancestors did it from time to time. A 7 day fast here and there is completely natural and not that hard after the first 30-50 hours.
Your point is irrelevant - the post you replied to asserted that it's tough to create a diet with no carbs, to which your suggestion is to not eat at all. Not eating is not a sustainable diet.
It is a sure-fire way to get into keto if that's your goal. Also there are some significant advantages to intermittent fasting vs continuous calorie restriction: https://www.dietdoctor.com/intermittent-fasting-vs-caloric-r...
On a keto diet, one can attain < 20g carbs per day with some struggle but to cut it out entirely is really hard without missing some other essential nutrients - because at least some carbs tag along with other things.