“I doubt the Russians would be so silly to send nuclear armed aircraft into someone else’s airspace”
If the story is true, and I don’t know about that, then the “airspace” would be the air above an island in the middle of the Baltic, so not exactly like sending your plane deep behind enemy lines.
Sovereign airspace can be defended with deadly force. If the Swedes are calling out Ivan for flying nukes towards Sweden then then next time the Swedes intercept the Russians in Swedish airspace it’ll be a fight.
And the Swedes hate the Russians.