I am still not quite sure I got the answer to my questions. When you say "move out", do you mean just moving the pointer outside of the machine window without clicking outside of it? And once the pointer has gone outside, can you move the cursor in the Notepad window with the first click, or only the second? And is there anything other than the auto-hidden menus in the machines that might react to mouse over movement?
I also wonder whether this has something to do with your Mate environment on the host.
5.1 Different behaviour
Re: 5.1 Different behaviour
A colleague failed to reproduce this with a fresh Windows 7 installation on Mint 18 with Cinnamon. Might there be something installed in your Windows guests which is causing this? Or are you able to try with a different desktop environment on the host (Cinnamon?)
Re: 5.1 Different behaviour
We also failed to reproduce this on Ubuntu with Mate. Perhaps you really have something installed in those Windows machines which is causing this?