Why one third of preventable hospitalisations are not actually preventable

There is one statistic frequently quoted as a measure of the success or failure of general practice care.
It’s the number of preventable hospital admissions: officially, those admissions that could have been avoided with the “provision of appropriate individualised preventative health interventions and early disease management”.
Policy wonks use it as evidence that more can be done to stem the tide of waste and avoidable suffering in the health system — evidence of a problem in need of a fix.
You can chop the numbers in various ways, but according to the AIHW there were 748,000 preventable hospitalisations in 2017-18.