This is brilliant! Sites like this remind me of what made the Web great: nothing to sell you, nothing to advertise, nothing to buy; just some nerdy amalgamation of the reboot sequences of yesteryear.
The Amiga one is wrong. It shows a 2.0+ restart window, but then does a 1.3 boot when you click it.
Edit: Also, there are some oddities with the Windows 2000 one. The gradient-bar... thing, scrolls from right to left, but it should go the other way. And the boot progress bar starts out solid and ends up dashed, but should do the reverse.
The XP one makes an alert noise, and then the shutdown sound. As I understand it, the error noise is some program crashing or showing an error in the background, but you can't see it because, well, it's showing that shutdown screen.
Also, on the Windows 95 and 98 ones, you can double-click an option to do that action - instead of clicking e.g. "Shut down" and then OK, you can just double-click "Shut down" to shut down.
Interesting to note the patterns of where you put 'default' actions.
Most of the Mac screenshots have the 'ok' button on the right, while windows is usually (but not always) on the left.
This is always a UX debate when designing something new, and you can always find supporting examples of doing it a variety of ways. It's a bit surprising that it still hasn't been settled after all these decades.
Maybe because settling UX decisions that have become part of habits, documentation and shared visual language in one environment in favor of the complete opposite would by itself be worst practice in terms of UX?
(see the changes of Windows' Start button and its surroundings and how users appreciated it)
"Sorry mate, but the Restart Page only works in desktop computers. We think that in order to reproduce the original rebooting experience you need to be seated in front of your personal computer, as we used to do back in our beloved Amiga Workbench days.
Press the button below to email yourself a reminder to revisit The Restart Page."
Meta and whiny trigger warning.
Not a chance. I don't do any casual browsing on my actual computer. Reading this has just made sharply aware of that, which is interesting in itself, so thanks, I guess!