Given that it held up against 13 years of dedicated efforts by people with physical access to the device, many years after its successor was launched, it seems merited in this case.
This talk about some of what went into it is fascinating: https://youtu.be/quLa6kzzra0
It literally got hacked, that's what the article is about. It is NOT unhackable.
"Extremely hard to hack" or "Hackable only after it's retired" don't exactly roll off the tongue, but they are not synonymous with "Unhackable".
In many cases the truth is simply that its not worth the time/effort to hack it, so only the most dedicated perverts(with a positive connotation) keep trying.