[question] why do 'locked' pinned? apps never stay open?

I hit the lock to pin my damn alarm clock open, I've tried many, need one with multiple timers..and they always never wake the phone, it ends up firing when I unlock the screen, every time.

Now a new issue, when I'm playing some music from the lock screen, any time I pause it for more than like a minute or few, it closes and will no longer respond to my headset or show on lock screen.,.

yes, battery optimizations are off, allow on lockscreen is set, and autostart is set, battery saver is never on

xiaomi 17