Hi JC.... welcome to the forum!
First lets define flushing as the act of pushing 3x the container size of fresh water through the soil, to cleanse the soil of all salts and left over nutes and debris. Flushing is not the act of starving your plants at the end by giving them only water.
Proper flushing (3x) is actually very helpful several times during a grow to keep the roots able to fully uptake the water and the nutes. Especially 2 weeks from the end of the grow, when the buds are packing on the most weight ever, a proper flush can be very helpful.
We now know that you can't starve the plant of nutrients at the end and somehow clean out the plant for better smoking. The only thing that clears chemical tastes is a proper dry and cure after harvest.
Hope this helped! Good luck with your grow!