I've recently switched from Lenovo A328 (Android 4.4) to Samsung SM-A320F (Android 8.0, not rooted). On Lenovo I had screen lock set to "pattern", and that let me get rid of the misfeature of opening global menu dropdown (don't know what it's called) which allows to do almost anything.
After switch to Samsung I discovered that "pattern" locker no longer protects from this gesture. After pulling down the global menu I can, for instance, turn on WiFi, toggle flash light, change brightness settings, even change sound mode. There are some things I can't do from there, but this doesn't help much: I can even reboot the phone* trying to extract it from my pocket!
I've managed to remove the Phone and Camera shortcuts from the lower left&right corners, but I still can do any other harmful things while lock is on.
So, how can I make sure that screen lock really locks the screen and keys until I trigger its unlocking? Only emergency calls should be possible while locked.
* or whatever it was: holding volUp+volDown+power pressed for several seconds resulted in some sort of restart