Not a Bluetooth expert and I might have misunderstood the paper but it seemed like it can be done any time two devices initiate a new connection (not when they'

Not a Bluetooth expert and I might have misunderstood the paper but it seemed like it can be done any time two devices initiate a new connection (not when they're paired but anytime they start communicating). AFAIU, it's a firmware level hack so not something you can do with standard Bluetooth functionality. You need to be able to get a custom firmware into the Bluetooth chipset to carry off an attack.