If a mobile phone is given a /64 that means that entire /64 is routed to the phone, so any attempt to scan it (even if it doesn't find the actual address in use

If a mobile phone is given a /64 that means that entire /64 is routed to the phone, so any attempt to scan it (even if it doesn't find the actual address in use by the device) will cause battery drain. But maybe attackers just won't even try.