It’s nice that you can shut down the Pi by pressing the button 5 times but how do you turn it back on again? Is unplugging the USB cable and plugging it back in the only way?
Hi, see https://raspberrypi.stackexchange.com/questions/5489/how-do-i-turn-on-my-raspberry-pi-after-shutdown.
Even though the button can’t start the Pi back up, the safe shutdown function helps protect the file system, so the OS remains bootable. 
It’s a pi inherent problem. To get out of the halted state you have to interrupt the power. Which means either a switch (actually ‘turn off’ power to the pi) or a relay or the like. The pi, to save money doesn’t include the hard bits to do a proper power cycle.
A solution I like to use, but haven’t tried with the pisound, is the pimoroni onoff shim. it’s small enough to fit between pisound and pi and get you a proper up and down. I just haven’t checked the pin assignments yet, but would guess they are free. Sadly, GUYS, the gpio diagrams from blokas suck. As soon as I sort it out (eg. create an overlay of the pin assignments), I’ll post.