With good drainage and warm weather, this might be a good idea to do for O2. I'd like to do that with my bin but it is 2' deep and the "wetness" might just prevent airflow.

When I feed melon it allows more water to pass thru the bin than I like . so I always buffer with extra newsprint when I do that. I have never flushed with water that would make a bin entirely too wet in my opinion. Unless its done for some other reason not mentioned.

I used to have a Can O' Worms and I don't remember that (pouring water through) from the instructions. At any rate, I never did it. It would make a big mess and serve no purpose.

Generally with the plastic bins, after you first start out with moistened bedding your need to add water above what comes included in the food scraps is usually limited. I suppose with a bin kept outside in great heat or wind that might differ, but indoors the problem is usually limiting moisture, not increasing it. I almost never add water to my current bin (Worm Factory) apart from some very occasional misting on new bedding.