You have to think of the person actually growing the plants. Someone who doesnt know what nute burn is or looks like, most likely will not know how to fix it and save their grow. Flushing will remove some of the nute's, there is no denying that, will it remove everything? No. If the plants are suffering excessive nute's in the soil it would only make sense to flush the excess out of the soil.
And as far as ph in soil, if I water my plants with a high or low ph water they turn to shit. I did not get my plants to look like this by not checking the ph of the water.
View attachment 2941652 Every watering the ph is 6.6
This is what I get by "not checking ph"
or giving them a ph they cant handle, in this case 8.5 water,
My plants do not tolerate a wacked out ph water. It is very important.