Keep in mind that the 5 billion figure is literally just from food insecurity and famine during and following nuclear winter.
More people would die in the explosions directly, and more would die from the resulting fires + building collapses + radiation fallout + infrastructural collapse.
Given that most targets are population centers and military targets (often both), it doesn’t look good.
But yeah I mean there probably would be some survivors.
One night, I went to a McDonald’s expecting the fabled Sprite I’ve had before, and I guess their dispenser ran out the syrup. What I got was basically just soda water, and it low-key ruined my night because we got it via drive thru and I didn’t take a sip until we got home 🥲