Not sure how they can bring a computer out of hibernation unless they keep some software running in ram. I know Windows 8.1 do not really close as default and still have stuff in a hibernation file, which is how it starts up so quick, but as far as I know the memory is empty.
Windows 7 never really have that mode, you have to put the computer into hibernation.
sleep mode is a different thing, that is when the machine rams is still kept alive, i know when my computer is in sleep mode as the power light keeps flashing, not that I put it in that mode very often and even when I am done using the computer, I switch it off at the mains and i have turned off the fast start up on Windows 8.
i just don't like windows 10 simple as that really, I tried it and did not like, never mind about the spying and other rubbish, I just do not like the UI.
I also do not see any advantage over 8.1 for me.
Desktop machine now powered by windows 8.1 pro 64bit, no dreaded metro, laptop by Linux