iPhone is very useable in lockdown mode. If you're paranoid or prefer security over convenience, turn it on.
Discussion
He is in lockdown mode now. He was paranoid before so now we stepping it up. If he didn't have 2fa and all the basic security set with face id etc he would have been taken for a ride by them.
So there was an actual attempt to exfil data or do something malicious to the device via an app that he had installed? What app?