you are most likely correct. Its either due to permeability or...

you are most likely correct. Its either due to permeability or thickness, but like you, i suspect it is the former. Transmissivity is the number that affects drawdown and it is proportional to permeability...and saturated thickness.

It is likely lower than expected permeability has resulted in the drawdown cone being too steep which means they're not exposing as much of the gas bearing coal with each pumping well as they had hoped/planned. One way out of this is to drill intermediate wells, which has the effect of "spreading" the drawdown curve. And they have said precisely this in their latest comms.

Its not the end of the world. Its just going to take a bit longer (and be more expensive) to get to the desired point.

The key to their success will be their ability to understand the permeability controls and to predict where to find the more permeable zones...They will need to target those zones with the next lot of drilling they do.