This is about tomatoes any relevance to pot?
“Flushing exposes hydroponic plants and systems to fresh, clean water instead of the mineral-rich nutrient solution that they normally live on. It is recommended as a way of keeping the pump, pipes and other system parts free of an accumulation of excess mineral salts, dirt and other debris, such as algae. Flushing also allows plants to shed any buildup of salts they may have, making it easier for them to absorb the nutrients they need. Finishing fruits and vegetables with a fresh-water flush also makes them more palatable and removes the bitter taste a salt buildup can cause.“
Half of this is good and half is a myth.
Yes flushing your irrigation system does help keep stuff from accumulating and eventually fouling out drippers/valves/pumps etc..
No you can not remove nutrients that are already deposited in the plant tissue. Pure water in hydro systems just starves the plant of everything it needs to function.
It's pretty much like putting a human being on a water only diet. They do ok for a day or so and then it gets ugly. Haha