I think Darwin ATIS might be using equipment on the airfield rather than the BoM equipment near the highway. More representative of what is actually happening at the airport. Especially with regards to QNH. Cloud and vis from the Met office is nothing like what it is in the 'real world'!!
Probably the same for many other places too. Met offices are not always located where they can see or sense what aviation bods need.
Sorry for the off thread stuff. Isn't Darwin a training venue for ATC? Might explain some of the sub-standard goings on? I've noticed a lot of difficulty with allocation of parking bays at times. How hard is it to look out the window and see which one is vacant?