A single button on the keyboard would be great for an OS login request or something to bring up task management.

A single button on the keyboard is utterly unsuitable for a request for soft reboot unless it is recessed and requires turning the keyboard over.

IIRC, other computers such as the Apple II had a single 'Reset' key. It was not uncommon (for me) to be typing in my code from a magazine, reach up to hit backspace (delete) and accidently reset the computer. :(

There were a few iterations that depressed the key, etc.

Overall, I liked the three finger combination because you had to mean to do it.

I will say that using it to login/lock windows instead of rebooting was not intuitive at all.

Sure. But what do you do about the tons of legacy hardware in the world?

The nice thing about the key combination is that the constituent keys are still useful on their own and in other combinations.

Bzzt. The correct answer is no button.

What is your conceptualization for 1 key being better than 3 in this context?