This could be measured as the MSU measured the plant tissue of orchids in the wild. Maybe someone should measure an orchid in culture and see if there is a difference.
The object is not to mimic Nature but rather develop methods that improve on Nature under artificial conditions. The mineral content of wild growing leaves doesn't necessarily mean that is what is best under artificial conditions. Too many variables to rely on tissue analysis...is it the same consistently in all seasons and climates and light exposures? Doubtful.
There is no need to test all variables. If paphs grow better ie. with high humidity than others should do the same and not expecting a fertilizer which will solve their problems on a windowsill. Thats ridiculous IMO. So testing fertilizers in a standarized condition which anyone can adapt to should be fine.
That depends on what results you want to end with. I am making the assumption that the desired result of the ST K-lite trials is to have a formula that is known to work well under a wide range of artificial conditions benefiting the hobby grower.
Of course with 500 plants you could get results and prove one set of conditions. That is what MSU did, they developed a formula that grew orchid plants rapidly to bloom. Their concern was to finish a crop and get it off the benches so another can be produced. They did not consider the long term health of the plants, it does not matter for commercial production. What mattered was planting a Phalaenopsis seedling and selling it in bloom in less than 2 years.
I'm not saying that controlled trials are not worthwhile (I've done plenty) I'm just saying that to the members of the orchid growing community this informal ST trial has more practical value.