There are a bunch of side-by-side taste tests that show that flush vs. no flush doesn’t matter much.
I typically stop feeding my plants 2-3 weeks before harvest. I suppose you could consider that a flush of sorts. Lots of growers do it. It saves the hassle and cost of feeding for a few weeks and nutes aren’t needed when all the plant is doing is ripening flower.
I fed my plants right up to harvest when I first started and I honestly can’t tell a difference myself. The early plants were smooth as well (given a proper dry and cure.)