As discussed in the article Will to really provide any "real" conclusive data, would require lab conditions and I would have to estimate 5 years. So no, the experiment is not still on going.
Several of these experiments have been conducted in the past, with inconclusive data IMO. One took place some time ago (info no longer available) at the old GCB site. Why the results were inconclusive is that feed rates were altered to suit the growing medium. IMO this should not have been attempted, because the results were indeed skewed and favoured the trees that received greater nutrition vice what the potting medium did for the tree.
In one of your articles it is stated that folks can grow trees in chards of glass and that is also true, any botanist worth their salt will support this conclusion as trees/plants do not need "dirt" to sustain life. They need oxygen first and foremost, water and nutrition.
In my experiment the feed rates were not altered and we can see the results. Where the tree planted out in straight gravel prospered the least. Is that data conclusive? Well yes and no. Could similar results when comparing with the other 2 be achievable? yes with a properly adjusted feed regimen because of the low CEC of the potting medium.
As discussed in the article, only the watering varied because of the water retention of the various mediums. I also flushed out the soil of "my mix" once a month, due to the high CEC of the medium to level out the playing field as much as I could, while maintaining fair play so to speak, to arrive at some sort of conclusion.
Th rest of my conclusions as you know are contained in my article's closing arguments. These trees are all potted up as we speak, one of them was exchanged with another fellow enthusiast, as a matter of fact, the individual that had conducted a similar experiment using turface ratios.