Hi,
It's not clear to me why you would attribute the growth rate to AS alone and not to EI + CO2. I can get amazing growth rates using inert sand + EI + CO2, so from that standpoint the performance of the AS would be overrated.

According to the most recent Barr Newsletter, AS performs about as well as lake sediment and not a well as the combination of garden variety potting soil+sand. In fact, the test results indicate that of the 6 substrates tested in the study, AS Amazonia came in 5th.

Enriched soils perform better than inert substrates, obviously, but a better test of AS or any substrate would be to grow the plants with minimal water column dosing as discussed in the Newsletter.

Cheers,