A friend of mine who has done many dry pours uses the repair mortar. He does 3 inch dry pour using the first 2 inches of quickrete concrete and the top inch of powder mortar and it comes out smooth

Should’ve topped it with sand topping mix.

Do the instructions actually say to get up in the middle of the night and water the slab? I'd imagine setting up an oscillating watering unit. The one that goes from say front to back and have enough of a stream coming out that water keeps it soaked overnight. And if your slab does crack, what do the makers say about any sort of warranty? Some money refunded? Time-frame before it's allowed to crack? Oh, wait you put a bbq grill on the slab? Oh, that's too heavy, you were only allowed to put a marshmallow sculpture on it. To this non-construction person, the slab looks great. Waiting for the firepit's transformation.

I doesn't make sense to me all these people doing "dry pours" Its going to be a VERY weak slab. Its really not hard to add water and mix, for something like that you could just mix with a shovel and a hose in the form. For something like that even a beginner could do it and be done in a couple of hours. It's really very easy, dry pour looks more complex for a weak end result.