A non-feeding Spotted Python taking a prey item scented with a rabbit does not sound all that unusual as far as captive snakes go. In captivity snakes will often take an item that you would never expect them to take in nature. Western Hognose snakes take pinkies scented with Tuna Fish - and I am pretty certain this is not a natural prey item for them. It is often a change that seems to trigger to feeding response. The item used to scent the food item actually may smell something like some other natural prey, or its scent may simply have a molecular makeup that triggers some response in the Jacobsen's organ and then in the feeding response as would a natural prey item.
As for it being difficult for them to take even a baby rabbit, maybe you are not familiar with the size of newborn rabbits such as wild cottontail rabbits as opposed to farm bred animals. They are pretty small and should be easily ingested by an adult Spotted Python. In addition, there are so many rabbits in Australia (introduced species with very few natural predators left in Australia), that it is quite possible that Spotted Pythons and other snakes have evolved or developed a taste for them to the point where the scent of a rabbit triggers the feeding response. Of course, baby Spotted Pythons would not be able to feed on the rabbits but, the trigger effect on their sense may already be bred into the pythons after many decades of rabbits running rampant in Australia. Just a hypothesis on my part.
best regards,
Glenn B