Same for me - has worked for a few years now. The only hitch is when I allow someone else to use the phone and they just put it down after use expecting the screen to lock automatically, which it won't...

I often find myself leaving my phone unlocked on the table while I do something else, knowing that locking it risks the app I'm using discarding my state so it can show me more Content despite me having more than adequate RAM. I don't have it set to Never, but it is longer than default to accommodate this.

I have to ask, why? I use the default settings without issue. Face ID is near instant, and I have almost never had my phone go to sleep when i don’t want it to.

I never forget to turn off my phone, probably because I'm so used to pushing the off button when I lay it down because I disabled auto lock on my first iOS device (1st gen iPod Touch). Maybe it's better now (by registering attention via face id), but back then I often found myself keeping something open as a reference and then having the screen turn off when I needed it.

edit: I just checked and indeed the settings screen says it watches for attention, so I'm willing to give it a try and enable auto unlock now...

What about when someone drives by on a motorbike and snatches it from your hand. A common way to steal phones.