I imagine they will be more selective and the event will still have billions of casualties – interesting alternative theory that the main winnowing will come prior to the pole shift

Indeed, this is the great mission: to preserve the species homo sapiens sapiens and its technological advancement. To thereby escape Samsara.

To preserve our technological advancement requires a manufacturing and power generation infrastructure that is operating now, and can continue operating during the pole shift and thereafter.

As for the species, there won’t be a ticketing system.

The extant population will have been winnowed down to tens or hundreds of millions (the capacity of underground cities), such that if you are still alive just before the cataclysm (ETA 2048), you’ll be ‘brought into the barn’.