Yes, and sometimes no. Try turning my mother’s phone off via the power button, it doesn’t work, because Samsung in their infinite wisdom made that the sleep/wake button and the assistant button.

I had to literally Google how to turn it off. Gotta hold Volume Down and Power at the same time to bring up the power/reset buttons.

So yes, they can be programmed, usually by the manufacturer though. Not like you can expect your mother or most any other average citizen to install, maintain, or configure a custom firmware.

And even if you do set everything the way you want, the next forced update is likely to revert to whatever the manufacturer thinks is good for you.