You can eat 5000 calories in one big meal after fasting, or spread put over smaller meals without fasting.

True, but the topic was "one meal a day of 1500 calories" for a muscular individual, i.e. fasting together with a calorie deficit.

Most people would struggle to finish a meal with half those calories, and rightly so - it's excessive. Strongmen could go over that amount a day when bulking, maybe, and that's about the semi-practical limits of the human body (while maintaining at least some semblance of health).

You are right about the fact this is fasting.

But the parent wrote "Does such caloric restricted diet allow one to maintain muscles and/or strength?" Which means he is asking about caloric restriction responding to comment about fasting.

I'd say the parent's question is perfectly valid: “He gets by on one meal a day of 1500 calories.” implies, in fact outright states, a calorie restricted diet as well as a temporally restricted one.

> Which means he is asking about caloric restriction responding to comment about fasting

1,500 calories per day is calorie restriction for an adult male of this size.