Hm. I can't "Hey Siri" someone else' phone, can I? It's certainly never worked for me.
The only problem here is that Google still doesn't recognise my voice half the time, perhaps because I'm never sure about how I should speak to an inanimate object.
Speaking of unlocking methods, face unlock appears to no longer be available as an option for me. I can't find it in settings anymore (smart unlock etc).