This is a warning that someone is trying to gain unauthorized access to your account. If the US government wants access it probably has better methods than brute force, such as ordering Apple to hand over your stuff.
I see no reason to think Apple will want to stay silent about an attacker trying to hack a user's account just because they might stay silent about warrants with gag orders.
When we're talking CIA, you can't get your way out of it with a better lawyer of by paying a fine. It's a decade of jail waiting for you if you don't bend over and give them exactly what they want. You have no constitutional rights when it comes to national security. they are legally allowed to kill US citizens without having to get court approval if they think they are a threat to the nation.
You seem to be talking about the first, whereas the support page is about the second.
Like it or not, if they go against three-letter-agencies in the US, high ranked apple employees will spend years in jail based on the rulings of secret courts where all of your rights are irrelevant. The moment the cia says the word "terrorism", all your rights are gone regardless of how wrong the investigators might be. They can literally declare you guilty without you even knowing you were were accused of anything because according to them, national security is more important than the constitution.
they are on the same level as the ccp