It won’t be this rate. It’s pretty much impossible to lose this much non-water this quickly - unless one does some extreme activity but that results in extreme quick muscle loss too and obviously it’s not sustainable… People doing a complete fast may experience this weight-loss but some of it comes back even then. As far as I know. There are too many factors, maybe it’s not true for everyone.
Even so, if much of this loss is water, it’s still very quick! And it’s just the weight-loss… There are other benefits. I only got fat adaptation and new recipes, some experiments from mere keto but those were nice too and I needed keto to go further eventually.