If there happened to be a spy among them, that person wouldn't be able to secretly communicate through mental links to coordinate any schemes against them. Any communication would have to be done openly, or through suspicious movements that would immediately draw attention.
And if there were multiple spies planted among the different packs, they would still be forced to interact in the open if they wanted to cooperate.
That alone would make them stand out.
Zion and Maxwell had been quietly observing everyone throughout the journey. If anyone tried to slip away under some excuse or behaved oddly, they would quickly notice and narrow down their list of suspects.
In this way, any hidden spy would eventually expose themselves.
Most importantly, this would likely be the last opportunity for any spies planted by their enemies to make a move. If they wanted to sabotage the creation of the teleportation portal, they would have to act now.
