Arduino AutoShutdown Using 5V DC Relay or MOSFET - Project

I'm learning how to use relays. I understand their basic function and have managed to build a few projects. But I came across an example that uses a relay or MOSFET to Auto Shutdown Arduino and I'm not sure if I've understood the circuit correctly. When I built this project, the Arduino powers off as soon as I release the button! THIS IS HOW I SEE IT: The relay (which is using NO) is initially LOW, meaning COM and NO are not connected and therefore the Vcc into Arduino's 5V pin is not going to

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