They are (or were, at the time they had that slogan) an Australian company. I am an Australian citizen. Under Australian Consumer Law, an advertisement is absolutely legally binding.
The link I shared makes it quite clear that "puffery" that nobody is reasonably expected to take literally does not count.
Being told that the app you paid for would be a one-time payment, and then having the service deliberately degraded to try and force you into a subscription model, is clearly not puffery.