I very briefly worked for one of their competitors a few years back. These devices are pretty much limited to whatever you can do with root on android or jailbreaking iOS. If a person has a modern phone and a good sense of op-sec, chances are they can’t get much. These things basically work by doing backups then analyzing those backups offline, searching in known locations for non-encrypted databases and images. On android they can also do things through adb, like automated screenshots.

If you hand the cops a powered off non-rooted,locked bootloader, non-jailbroken phone and use e.g. signal, there’s not much they’ll be able to see. Of course, there seem to be other firms that operate at a higher level, and have some encryption breaking capabilities, but that’s not going to be accessible to your average cop.