I really think this depends largely on who you are and what you do with your phone. I have face recognition and fingerprint recognition both enabled on my phone. It's good enough to prevent a thief from gaining access to my device, and if law enforcement asked, there's nothing on my phone that could possibly be incriminating. Realistically, I'd have no issue just unlocking my phone and giving it to a police officer, although I do know well enough to always get a lawyer first. Biometrics add an extra layer of convenience; it's nice to just look at my phone and it unlocks. My concern personally is more about someone stealing my phone and accessing my accounts than self-incrimination.
If I ever was going to put myself in a situation where I'd run afoul of the authorities, I'd leave my phone at home anyway.