Flushing is not just running tons of water once. Flushing also refers to this not giving nutes for the last some days. Flushing some specific nutrient out thus is leaving it out near the end.
Im talking about this:
"You're going to do everything you normally do when it comes to watering, except without any additional nutrients or supplements. Don't give more water at a time than normal, because this increases the chances of your plants getting
overwatered and showing
deficiencies/symptoms caused by that problem."
Some nutrients dont need this, some definitely need some and in some situations its best to just tune down the amount of nutrients, not stop them completely.
My point with this topic is that there is no yes/no answer to flushing, but it depends whether to flush or not, how long to flush and what to flush.