I always put my computer in standby mode, and I have never even given a second thought to the idea that it wasn't "completely off."

You're right that it isn't completely off; I just never gave that any consideration. I'm sure I"m not the only one making this mistake innocently.

(FWIW, ever since I installed the company's PC encryption software, hibernation mode doesn't work too well, so that's when I stopped using it.)