The article didn’t actually supply any data, just sweeping statements that are as inaccurate as the idea that more organic matter is always beneficial, from my reading. Organic matter doesn’t necessarily bleed either N. or P even in beds of pure compost, and no results of research studying stable compost was provided in the article to demonstrate that it does.
Slow release N can contaminate if plants don’t seize it before it goes below roots or into waterways, so the theory that this sometimes happens in gardens is sound, but I’d like to see the research. I long ago saw research that harmful leaching of organic matter N does occur after fires in large areas, but that’s a lot different than a small vegetable garden.
Once P binds with soil, it is mostly immobile except through erosion, as I understand it.
For fruit growers in the humid regions I believe the key danger is that high organic matter in the soil greatly expands the amount of available water, which can make fruit big and watery and also encourage excessive vegetative vigor- depending on rainfall levels during the ripening process from about 6 weeks before harvest on.
As far as growing vegetables in pure compost, I’ve seen gardeners doing this for years for potatoes and carrots and getting incredible production. The burned pepper plants in the article were probably because the compost had fresh animal waste in it or some form of quick release N. That’s the only thing I’ve seen burn roots. Poor drainage could also explain bad results.
And too, nutritional balance needs to be considered with all soils, regardless of OM amounts and given the high nutrition content of OM the danger could increase as OM rates rise, but I’ve rarely seen it. More often plants suffer from nutritional deficiency than excess. However, I do suspect that excess K may lead to an inability of some apple varieties prone to corking to process calcium properly. Composts do tend to be very high in K.
Last season I applied foliar manganese on apple trees prone to corking and seemed to get much better pack out of sound fruit. These trees were growing in soil with excess K and I have posted on this forum an article by a commercial orchard consultant that manganese neutralizes the consequences of excess K. .