I thought that they said that a couple of weeks ago. It's really just stating the obvious. If Finland tries to join NATO, they will instantly have several nuclear warheads pointing their way, with Helsinki on the address label. As every NATO member already has. So everone in Helsinki will enjoy the privilege of being minutes away from being vaporized. That's the real security blanket that NATO provides.
I personally live ten miles away from the UK Government Communications HQ. A dead cert for one of the first nukes. It gives me a warm feeling. Hopefully, that's as warm as it will get.
If I was in Putin's shoes, I would just announce that Russia would not recognise any new members of NATO, and would treat them as non-members in any dispute. That would make things a little more tricky for NATO's enlargement ambitions, raising the stakes in the game of chicken.