I have a hard time following the arguments for/against because they often sound religious in nature. What you said reminds me of something which implies merit in flushing (especially for those who do the mutli-bottle "lineup" regimens, heavy feeding, boosting, etc.).
When there are nutrient deficiencies we hear about mobile nutrients being consumed(?). Like, N coming from lower leaves? It makes sense to me that flushing (or better yet, not overfeeding so much to require flushing) and/or reducing nutrients the last 2-3 feedings could improve performance (if salts were so high in the soil as to create acidity, impede microbial health) and taste (if the plant was approaching toxicity levels?).
I and others noticed a taste difference when I switched from GH 3-part (all synthetic) to Grow More Sea Grow (some organic sources, and I supplement with organic sources). So, it seems indisputable to me that something gets into the plant which affects taste.
I think the problem is when flushing is stated as a must-do (always helps) practice. I think it depends on the nutrients (if synthetic) and style (force feeding, over feeding).