I agree with this statement. Seeing that the Z9 mini consumes only 300 watts while in operation, it tells me that this miner has a small handful of ASIC chips inside. Bitmain has definitely made this miner underpowered, which is a good strategy since it's still enough to wipe off all GPU's anyway, and still give the owners of these miners a reasonable profit. From a marketing point of view it was a great move to not build their most powerful ASIC at first, and instead released an underpowered one at a hugely inflated price with phenomenal margins.

If Zcash doesn't fork, they'll come out with a more powerful variant with a TDP of 1000-1600 watts, and it'll be 5-10x more powerful but with similar efficiency ratings, and probably a similar pricepoint. Bitmain's playing this game smart.