Presumably exfiltration would work for most people, no? It is quite unusual to have physical access to a computer, and if you do generally all bets are off.

This is just the hypothetical situation where ransomware is a static binary that doesn't care about any data exfiltration - it just encrypts files in-place with a pre-defined public key. So no exfiltration, physical or over the internet, is required.

Ah, i see your point.