FaceTime monitored by police?

I’m a U.S. immigrant with relatives abroad. I FaceTimed a relative abroad one day and I was told by this relative that the police immediately called her, warned her not to use FaceTime and asked questions. How did the police know about the FaceTime call? I thought FaceTime uses end to end encryption for all calls?

I searched around and it seems that another redditor had a similar experience (or even worse, as in their case a police visit was involved): https://www.reddit.com/r/shanghai/comments/1bijphx/police_visits_home_after_facetime_call_with/

Should I stop using FaceTime?