You know what's weird? The only communication bitfinex is having with the outer world right now is through a community manager's Reddit account. Has what this user been saying confirmed?
https://www.reddit.com/user/zanetackettI would guess that everyone else is trying to figure out what exactly happened. Based on their public statements, they do not know how the attacker was able to gain access to both the "hot" signing key and access to BitGo (and get around the signing restrictions that they had with BitGo).
Might just be an internal job for all we know. Seems to be a trend now-a-days claiming to be jacked when things are actually not going on so well internally. Just my 2 cents.
They seem to be fairly confident that it is not an inside job, at least based on their community manager's reddit posts. I would guess that they have some amount of information that suggests that the attack came from the outside.