I don't think it's
all hype. But I do think the benefits some growers see when using Mammoth P are more due to the 2% alfalfa extract (triacontanol) it contains, rather than the 1% bacteria culture. When I tried it in my organic room I didn't notice a difference on the plants that were given Mammoth P vs the ones that weren't. I attributed this to not using any high P sources to begin with, and I was already using multiple products that contained alfalfa extract.
Most of the guys that swear by Mammoth P are running salts or full synthetic liquids. Like someone else said, not an ideal environment for microbes. Also, many salt/synth growers use products with sky high P/K levels, but not necessarily any products that contain triacontanol. Most of the claims on the Mammoth P bottle (16% yield increase, better stength, etc.) are exactly what happen when you use triacontanol. Check the wikipedia entry for it:
https://en.wikipedia.org/wiki/Triacontanol .
Most organic growers are already using at least one source of triacontanol, hence they don't notice much a difference when adding Mammoth P. Bottom line, I'm skeptical the bacteria has much to do with the success Mammoth P has seen thus far. This is all just speculation and based on my observations and interactions with customers while working at a large hydro shop for years. So take it for what it's worth.