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.)
Plant scientist show that most of what you wish to " flush " is imobile. In other words, its pretty much locked in. When a plant is in senescence it isn’t uptaking nutrients anyway. Even water uptake begins to slow. You can think of it like a person nearing death, they typically start eating less, eventually it’s down to trying to get a protein shake down range, and ultimately sucking on an ice cube. Plants are very similar. When its time to harvest, its time to harvest, the biology is turning towards decay. The trichomes begin to turn dark amber and eventually fall off the plant. The good news is that flushing may not be bad for your plant, its dying anyway. The bad news is that if you grow in soil with good drainage you are flushing out nutrients, if your soil has poor drainage you create an anaerobic environment. In a liquid hydroponic system it really doesnt matter because feeding a dying plant is pointless anyway. So do what makes you happy… if you feel it makes a difference then it’s part of your process and its all good! I will be growing in living soil, so flushing is a bad idea full stop!