I'll leave the keto for another thread, you are right but for some people it is incredibly effective even once that water has gone.
I'm not disputing keto or low carb diets for their efficacy in terms of weight loss, merely stressing that notable losses early on are largely water, that's all.
And let's be clear on keto / low carb diets, they can be effective for many, for several reasons (hormonal response, satiety, adherence, preserving lbm) - but all other things being equal, there's no tangible / significant metabolic
advantage (that matters a damn over normal time periods) for ketosis for weight / bodyfat loss.
I know if we talk pure xc, long rides then body weight is going to usually be a win with the fitness from the exercise a byproduct but in other disciplines it is less relevant. In general freeride on a 35lb bike, if that weighed 30lb would your ride improve all round more?
All I would say, is that in appearing, generally, biased in terms of focus on bike weight, you seem to be saying: "let's forget about all the tangibles, and focus on all the intangibles..."