Basically they want the new season jersey's in pre-xmas for xmas sales, the manufacters always blame the clubs and the clubs blame the manufacters.
A perfect example was the Tigers jerseys in 2006, the tigers changed sponsors last minute and didn't tell XBlades till after the order was sent to China to be manfactered and they managed to stop the whole order from being made but quite a few were made that Blades got stuck with. ISC make all their jerseys here so less chance of problems like that.
Last the Bulldogs jerseys weren't in stock til mid May due to a sponsor change that the club didn't finalise til Febuary, Nike wanted file comformation in Nov/Dec but the Dogs hadn't signed the contract yet so Nike wouldn't make any til final comformation for fear of being stuck with obslite goods. But by doing so cost them heaps of sales.
The NRL themselves have to finalise everything and that seems to take them a month and heaps of NRL merchindise is delayed all the time.