This is a potential problem with this implementation. “You are doing it wrong” is rarely the right answer when the same problem shows up over and over again. Especially if the only way to do it right is to know and understand something as arcane as the difference between reboot and shutdown -r, something that, based on a quick poll of heavy Linux users I know, only one out of 8 was aware that there even is a difference. It doesn’t seem fair to blame the user for not doing it “properly” when knowledge that there is a proper way is not general knowledge.
And the answer of “you should never reboot or shutdown” is also not feasible. There will be times, rare though they may be, where a reboot or shutdown will be required.
And we still have the problem of power loss. When running headless, no matter the risk, there will be times where the only choice is to pull the power, e.g. when the machine is otherwise frozen or unreachable. I’m not saying that zram should be able to handle that problem, but to insist that it would never happen is not reasonable. There should be at a minimum good documentation to explain this (zram is not mentioned at all in the OH docs nor in the openhabian README.