Most of these “You absolutely must” are a load of horse shit. My favorite (I even did a video on IG about it) is that you have to “gently” reintroduce food. I’ve done 3 day water fasts and went straight into heavy meal. I just came off of a 31 hr water/dry fast and went to a heavy meal. Zero ill effects.
I think it is just a suggestion.
Typically the Russians suggest you gradually reduce your food intake before a fast, with barely eating anything the day before. And then enemas before and during a WF (but not before a DF).
I have mostly started my fasts after a pretty good meal. I started the current fast (89h soft dry fast right now) with eating less than typical the day before–mostly apricots and prunes juice + psillium + raisins + dried fruits with a bit of honey concoction (which I love lol). So the idea was to naturally clean out a bit.
I didn’t notice any difference on how I’ve been feeling. I am feeling just fine, like almost always on a fast.
My longest dry fast was 4DF+4WF and my longest fast was 2DF+8WF. I’m not sure what I’m going for now yet, but at east 7 days total.
Good luck with your fast!