This guarantee doesn't scale very well considering the combined 5 Eyes intel budget is ~60 billion USD and throwing just 0.1% of their budget at negating Tor would completely overwhelm the network with hundreds of thousands of stooge relays, plus they have the added benefit of global backbone cable traps. Tor can't give any kind of guarantee against a global passive adversary (5 Eyes) which is why they specifically warn against believing otherwise.
This guarantee doesn't scale very well considering the combined 5 Eyes intel budget is ~60 billion USD and throwing just 0.1% of their budget at negating Tor would completely overwhelm the network with hundreds of thousands of stooge relays, plus they have the added benefit of global backbone cable traps. Tor can't give any kind of guarantee against a global passive adversary (5 Eyes) which is why they specifically warn against believing otherwise.