There's no need for a pre-harvest flush, I found out by accident when I had to pull a couple of plants 5 weeks into flower cos I got paranoid, I just let 'em dry for two weeks then cure for another two, that shit was just as potent as anything else I've grown that finished with a 2 week flush at the end.
Half the taste comes from genes, I would say, and the other half from a good long cure.
Hell my mate even stopped flushing his hydro plants when I gave him a bud to try, he flushed one tray and not another that were same type, same mother, same conditions, same cure and we couldn't tell the difference. If you can you have better tastebuds than ours!
Edit: That's not to say don't flush, just not neccessarily right before harvest, those extra 2 weeks of nutes the plants get help the buds grow fat and dense, if you flush it's forced to consume itself to survive.