For a start that's a BIG exaggeration (at least here in the U.K) NO police officer can walk into a room with your mobile phone and place it in front of you, with the intention of getting you to unlock it or not!!! secondly if your spouse girlfriend/boyfriend is that untrusting that they trick you into unlocking your phone (which may not work anyway) then you more issues to worry about, trust being one of them!!
People need to stop with this silliness, the exact same thing happened before Touch ID was announced, people were posting on this forum how others could cut off your finger in order to get access to your phone and so on, it was nonsense and people took to Touch ID like a duck to water. Apple know what they are doing IF Touch ID is being replaced with facial recognition then I'm sure Apple have locked it down, gone through a lot of issues and thought about a lot of situations in which people will be using the phone, if after Apple announce everything on stage at next months event people are not happy, don't buy the iPhone 8 no one is forcing you or anyone into anything.