If a comparable number of Xboxes were compromised through a game on Microsoft's own Xbox store then I would say that's an Xbox hack. It'd mean that the malware evaded the Xbox's security mechanisms (which are implemented at Microsoft's end when publishing onto the store).

For non-walled-garden platforms, like most desktop operating systems, a program being available for download isn't yet a bypass of any security feature. It'd have to do something forbidden like privilege escalation for me to count it as a OSX/Windows/Linux hack.

If Microsoft in numerous court cases had said the reason for the walked garden is because it is safe, then yes. But only Apple says that. This is not comparable to downloading for Windows but more like downloading malware from the Xbox or PlayStation store. Apple approved those apps.