It's not an exaggeration and probably a conservative number.
The think tanks quietly concluded this thirty years ago but it is a figure which has never been widely publicized until now.
There is no such thing as nuclear winter. Ash from atomic detonations is not projected high enough into the atmosphere to stay afloat for much longer than two years at the outside, no matter how many went off. Only volcanic eruptions can do things like this because they can accelerate ash to nearly escape velocity.
For that two year period, however, it would be nuclear winter. If enough nukes went off, it might be darkness at noon for two years. Such conditions would never persist twenty years as described by Carl Sagan and his soviet handlers. It is impossible.
Two years would be sufficient to kill a majority of the people on the planet from starvation and extremely cold temperatures.
Ordinary people cope with this reality by avoiding thinking about it altogether.
What if it isn't a limited nuclear exchange? What if it is a cobalt-60 death shroud surrounding the planet for a long time destroying everything topside, plants, animals, anything not inside a vault?