I believe this is just if it's sleeping with the lid open. If you go to Apple > Shut down... and let it complete, it will not turn back on unless you press the power button.
Nope, not anymore. This used to work for my 2013 MBP, but even if I completely shut down my M1, it will start booting upon any interaction. Opening the lid => starts booting. Pressing any key => starts booting. Clicking the trackpad => starts booting. Which is funny, because the trackpad doesn't physically click anymore, it just reacts to pressure, and only if it's a finger pressing on it (you can't click it with any object), and all that it still working when the computer is "shut down", i.e. you can't click the trackpad with a pen, but you can with your finger and it will turn the MacBook on.
Same issue here. 2020 Intel MBP, and when fully shutdown, pressing any key will turn it on. I would far prefer have a single, explicit power button. They even have one that seems as if it should be the power button (the touch ID sensor/key).
That's a bummer when you want to go clean your keyboard and don't want the laptop running at the same time.