But there's also "presumed" and "did not think" in there. When there's a problem with your killing device you probably shouldn't use it until you've clarified what the problem is and don't just assume your end users will use it correctly.
That's like saying "It's fine, the critical vulnerability patch will be applied on reboot", while in reality all your users just suspend to disk and move that annoying reboot nag window behind the task bar where it's out of sight.
Clearly the vendor thought it would be reasonable. They failed at communicating it, though. Putting a number on it would have made things clear: “The system must be rebooted after at most 12 hours [or whatever the appropriate value would be] of operation.”
That's like saying "It's fine, the critical vulnerability patch will be applied on reboot", while in reality all your users just suspend to disk and move that annoying reboot nag window behind the task bar where it's out of sight.