fasting to loose non-functional muscle

So a bit of background,

I had read an article about fasting to loose non-functional muscle mass here (used in cyclists in the article to loose upper body muscle), And wanted to apply it myself to help improve my strength to weight ratio in my climbing. A bit more background, I have been fasting on an off for mostly health and ethical reasons for max 3 days at a time. I have large leg muscles from cycling and rugby playing as a youth.

Whilst performing the initial ‘rough sculpting’ of the article, I certainly lost weight. I maintained an 80% calorie deficit, with the 20% coming from whey protein, yoghurt and pumpkin seeds (for the leucine), and lost around 3kgs (from 70kg to 67kg). And measuring my leg circumference, I got a reduction in length, 56cm-54cm.

However, since moving into the ‘polishing’ phase (maintaining a calorie deficit around 490kcal) per day to loose around 0.5kg per week, my weight has increased again to 69kg and my leg circumference is back where it was. I am still working through the ‘polishing’ phase and don’t have any data on the outcomes yet.

Can I assume that the real weight loss from the ‘rough sculpting’ was actually 1kg and the rest was water weight that has since increased after the fast? Do you have any reason to think this is a pointless exercise? would there be anything you’d do differently?

My weight not too long ago was around 67kg, I’m not entirely sure where the increased weight has come from, but I’d be keen to loose it to help my fingers a little bit whilst climbing!

Thanks!