Frankly that makes no sense in the context of a bodybuilder.

All of those studies listed in the review you posted are targeting either overweight people or "normal weight", both miles away from the body composition of a bodybuilder.

You can't take that and try to apply the same results to someone who's got their diet, exercise, sleep, daily steps, even salt intake dialed in like a bodybuilder does.

We all accept there will be muscle loss when you diet down. Heck, most natural bodybuilders probably have to drop 10kg before they are ready to go on stage.

I was speaking more generally, not necessarily in the context of competition bodybuilding. Should have clarified.

Keto is terrible for gains. I call it a "no gainz diet".

Source: I'm on long-term keto for reasons unrelated to weight.

It’s absolutely wonderful for long distance endurance athletes because you no longer have to either suffer through that period where your body switches to burning fat or otherwise keep taking in carbohydrates at steady intervals. It does however, as you say, absolutely suck for weight training. I did it for about two months whilst I was doing both weight training and triathlon training and my weight training sessions were awful. I reckon I was at least 10%-20% weaker on it than previous, maybe more. Cardio was a blast though.

You need a better source, my dude. And probably more protein.

Not an endorsement, but there is a sub: /r/ketogains I think they do controlled carb eating while on keto.

I'm only doing normal keto so I only have cursory knowledge about this sub and know nothing about the science.

ketogains is a good protocol. That sub makes me /groan tho.

TKD/CKD are variations which incorporate controlled carb intake to promote rapid glycogen recovery. Most people aren't training hard enough to need this.

What kind of fat reserves do you think competition bodybuilders normally have?

Also note that dipping below some level of body fat is actively harmful to your body.

Like voytec said, 4-8%. Though i’s argue it’a likely in the higher end for naturals. It’s not sustainable and it’s definitely not healthy for long periods. That’s why we do it only in contest season. You do your shows and get back to something reasonable in terms of body fat.

Most people only compete every few years

Usually it's something between 4 and 8% but I wouldn't call it "reserves". That's already too low.