I get why they can't provide details. But a close read of that incident report doesn't answer whether they even know how it happened. Did I miss something?
If LastPass says "Attackers took everything" when the attackers only took a few non-identifiable pieces of info; it will be a huge non-recoverable media event about attackers taking everything even if it's not true.
If LastPass say "Attackers didn't do anything" but stole a lot of sensitive info, then it makes LastPass look incompetent.
This is really a situation where they need to understand the scope of the situation before making a detailed comment.