I’m not someone who works on the practical side of security, but as a computer scientist, I do not agree that it is “hacking”. That contradicts my understanding of “hack” versus other types of exploits, but you are correct that the distinction is generally not that important. A security problem is a security problem regardless what it’s called
I’m not talking out of my arse here either. I don’t work in security specifically but I’ve got a CS degree as well and it contradicts my understanding of how those terms are generally used. This is an open API endpoint, equivalent to leaving the garage door open.
But the distinction is usually unimportant. A security hole is a security hole regardless of what you call it.