I'm not sure you can accept this as an answer, but maybe you need to know what happens when the pi is powered off as by disconnecting the power with a mechanical switch. For my purpose I needed this approach, so I gave it a try recently.
I placed the switch between the 5 volt cable. I didn't get in trouble after about 50 times toggling between "on" and "off".
Also I tried to switch on/off with really quick intervals, specifically when the file systems were being mounted.
After each "power off" without issuing
shutdown -h now
the 'dirty bit' was discovered by fsck at the subsequent new boot, and this bit was nicely fixed when the above command was used.
So, my conclusion from practical experience is that it seems safe to power off the PI by disconnecting it from power.
I'm curious what others have experienced, and if the PI is actually designed for this kind of brute force power off.
Having said all this, I think it is best practice (and best education too) to let any system have a decent way of dealing with its logic and current operations, before the power that makes the system possible in the first place gets interrupted. Information might get lost or corrupted otherwise.
Thanks for asking the question