[ridaj]

I can only guess, but I suppose the context in which they would trigger something like this would be that some of their accounts get hijacked to send things to a bunch of email addresses, which later turn out to be links to zero-day exploits attribuable to state-sponsored attackers, so they warn the recipients of those emails. But it's got to be a relatively scattershot warning - Google doesn't really know how vigilant you are. A friend of mine working for an NGO got the Gmail warning back in 2012 and upgraded a few overdue things.