Hacking can be defined as "using a system in a way it was not intended to be used".
In that sense, it was hacking.
In that sense, it was hacking.
But can it be considered a bug if it's inherent and unsolvable in the system? Can AI truly ever be resistant against prompt injection or will it always be a series of patches to cover up unwanted behaviour? (Genuine question - I do not know)
If something is inherent in the design of the system I'd argue that it is not a bug and not hacking, just as it's not "hacking" to use a hunters rifle to shoot a human, despite it being "not the way it was intended to be used". It can still be illegal of course, but that's a separate issue.
More colloquially when someone says: 'someone tried to hack us', it means the hacker tried to gain access to the companies backend servers.
Otherwise the court document would read "NYT paid someone to creatively create a solution to generating copyrighted text" and would actually be praising NYT for that, instead it reads like they are damning them.