Damn it, I didn't mean to power you on.
Yes, any system which is going to engage in some long activity which will freeze up the system for more than a few seconds should offer a way to cancel, abort or undo it. You would think designers would know that by now.
My latest peeve is cell phones and other smart devices which are complex enough to "boot." now. In many cases if you want to see if they are on or not, you touch the power button -- and if they were not on, they start their 30 to 60 second boot process. Which you must wait through so that you can then turn them off again. On some devices there is still a physical power button (and on many laptops you can fake one by holding down the soft power button for 4 seconds) but that's not a great solution. Sure, at some point the booting device reaches a state where it can't easily abort the boot as it is writing state, but this usually takes at least several seconds if not much longer to reach, so you should be able to abort right away.