The age old question.
Personally, I feed water the last 10 days or so, depending n the strain. I would not say that I am flushing, as I am not getting a ton of run off from the pots, just feeding plain PHed water.
I don't do this for the taste as much as the swell. I have noticed that when I feed just water the last days, the calyx swell a little more and a little faster then if I was to feed regular nuit mix. This, in turn, increased my overall weight. We are talking grams, not lb's. Bigger the room, more grams gained.
I use Promix as my medium, growing in 7 gal grow bags. I usually feed nuits 2 times, then water 1 time throughout the grow, from Veg thru week 6-7, then feed plain PHed water. Works well for me.
For me too, at my scale, usuing water the last 10 days or so saves on nuits too, which is a cost savings, as I don't see a need to feed hot mix to the end.
DWC is different imo. The uptake times for DWC is instant, so I would run nuits till the end. In my 7 gal bags, the Promix retains enough nuits to keep on feeding for quite a while by just adding water. Does this make sense?
But I agree with THG, it is near impossible to distinguish between well grown herb that has had nuits to the end vs water at the end.