Attackers are not necessarily going to be using the website 24/7, but posting an announcement to a place that is specifically for announcing outages is something that may give an attacker an alert.
I fully understand the seriousness, and the amount of money at stake. If you read that post I shared, they gave their policy on this type of thing. What you (and other users) want to happen in order to feel more safe is actually something that would make you less safe. Given the seriousness of what is at stake, not communicating anything until the situation is under control makes a lot of sense.
What you're saying makes a lot of sense, @timcliff. Thank you for your helpful explanation.
Thanks Terry :)