There is some evidence that appears to support the idea that there is a difference between calorie restriction and complete fasting. You sound like the type of person that likes to dig into the studies. Dr. Jason Fung does a good job of writing in plain English while linked to and referring to the supporting studies: https://www.dietdoctor.com/fasting-muscle-mass

The studies may not have been conducted among athletes so, testing your own body's response (by measuring lean body mass before and after a fast) seems like the best way forward.

I have read that people on keto diets or fasting have less "explosive" energy for workouts. I am not concerned that my body is going to cannibalise my biceps if I don't eat for a day or two. There is a lot more energy kicking around that is less important.

For me, it's worth it for the HGH boost: https://www.dietdoctor.com/fasting-and-growth-hormone