I don't know and couldn't guess the reason, but given they're staking their credibility and potentially putting themselves at risk of retaliation (see: Sony), I

I don't know and couldn't guess the reason, but given they're staking their credibility and potentially putting themselves at risk of retaliation (see: Sony), I suspect they think they have a good rationale for saying it. Perhaps it could be to gain a bit more trust or respect from researchers (targeted or otherwise) and/or certain customers/users, or perhaps the US government encouraged them due to some geopolitical calculus, or maybe it's part of some plan that only makes sense because of some private knowledge known to few.