"That job was very hard."
I wouldn't call it being "strict", but more that if there are a lot of possible answers, there's no way that the contributors can think of them all on their own. They need your error reports to add missing answers, and I'm sure the answer you gave will be accepted eventually. Other things to consider are that すごい is rather colloquial, which might be a reason why it's not accepted, and I find 非常に to be more traditionally translated as "extremely" to show that it has a stronger emphasis than とても. You can always submit error reports on those and see what happens.