Alright then. I opened my front door this afternoon to find a bright red, 5 gal bucket from aquariumplants.com.
Here are the pics of it compared to Turface Pro League...
The only difference I can see right off is that the Aquariumplants.com substrate seems to have less small grains (~1mm) than the Turface. But aside from that they appear to be identical. So maybe it's Soilmaster Select instead?
Seeing this, I'm not going to bother doing any extensive testing since there's abundant information already posted on using Turface/Soilmaster as a substrate.
I hereby relinquish my "David Horowitz" credentials.