Number of pings is dependent upon number of people who have tested positive and use the app along with how many people they interact with. Since Freedom Day people are far more likely to be going out much more and meeting more people, therefore the number of pings was always likely to go up considerably. I.e. the scale of increases looks to me to be led by changes in human behaviour.
But overall, no one knows accurately what is going on, despite all these varied data sources.
Whilst hospital admissions are related to the number of people infected, there is no direct correlation (i.e. back calculation of population infection is prone to large errors) because there are too many other factors involved (vaccination, human behaviour, variant infectiousness, population density, delay from infection of around 10 days, etc). But they are the most reliable numbers available to us as to the consequence (and the number of deaths) of the virus being in the population.