Assuming the plants are healthy and no reason to flush otherwise...
It doesn't impact mineral content of the flower (lab measured proof and common sense given existing knowledge base). This is how cell differentiation works. Flower is not a storage facility in the plant. That is not its function. The plant has no way to excreted nutrient molecules. Flushing phyiscally cannot change the mineral content of what exists in the plant. Impossible.
Also, drastically shifting the chemistry of the plant probably isn't optimal.
This is not a logical argument (doesn't mean it can't be highly correlative), but ... do you see people flush plants outside? Of course, not because it'd be absurd.
blind taste tests show people have no fucking clue which flower is 'flushed' or not.
Yes, i've done it. I'm a bit embarassed i engaged in bro-science, but it happens.
I've done it since learning better, because i'm a lazy fucker that didn't feel like mixing up nutes and my canopies are most often strong and healthy enough to do it. This does not embarass me, lol, because i did it knowing it would have zero impact, give or take. Probably more efficient to get nutes from roots than to cannibalize leaves, but that is a guess. the extra steps invovled would require more ATP, which is the primary energy currency in the plant. That's the sugar that photosynthesis produces.