I'm curious why you keep bringing up the "flushing" issue, knowing full well that what you call flushing is completely different from my #noflushclub links, something I am clear about whenever I post it. Maybe that's why no one "calls me out" on it. The people who I'm talking to understand the difference, where you don't seem to.
Buffering in the media is what allows growers not to have to pH their nutrient solution. There is nothing magical about ProMix. It's the reason that lime is added to soil. And I am waiting to read the link that says that the type of chelation changes the need to pH the nutrient solution. Since you have done all the reading, please let us read it too.
Please keep in mind that this is a discussion about plants grown in solid substrate like soil or ProMix and does not apply to hydro such as DWC, hempy, or coco, as I mentioned in the opening post.