Notes from AGM, page-25

Gimo,

i think you are best to go back and read a bit more. they have talked about measured expanding drainage area many times in recent months. On the evidence - i guess we will have to trust them (or not) that what they are putting in these reports are real.

Also, They have had many desorption events but that gas is being produced from coals that are closest to the well bore. Each time they draw the pressure down the coals closest to the well bore (and progressively further in on each desorption event) have been depleted of gas. Therefore it takes longer to re-establish that gas flow each time they get back to that point.
For the jet pumps i also believe it comes down to what nozzle is being used. If a large nozzle is used then it may shift a lot more water but may not lower the downhole pressure significantly. Whilst a small nozzle will flow less water but will drop the pressure immediately around the well bore more quickly. In the later scenario you get much faster gas flows but the pump cavitates faster and the coals further out dont dewater and ultimately depressure as much as if a larger nozzle was used.

I think they are probably taking the longer way around this time as they have big pumps, bigger nozzles (probably) and are looking to depressure the reservoir drainage area more "broadly" rather than just at the small area around the well bore. If so then it takes longer because of that pump set-up and longer because the gas contained in the coals immediately at the well bore has been desorbed already (in previous desorption events).
They probably went the other way to start with as they didnt have the pump capacity to dewater at a fast rate whilst also bringing the well bore pressure down. Therefore cavitation was always going to beat them before a commercial threshold rate was reached - even though the gas came on quicker.