Really, it doesn't make sense to you that enter would correspond to the most common, least destructive action?
Alt-F4 makes little sense, true, but in almost all windows apps control-q or control-w does exactly the same thing as on osx.
Also, having sane defaults for keys people are likely to press is much more important than /not/ having obscure keyboard shortcuts that users never have to know even exist.
I want to say ctrl+q is an exit command from within the application (graceful shutdown) whereas alt+f4 is more of a system level halt for whatever is in focus (hard reset).
That's not actually true. Alt+F4 is exactly the same as clicking the Close window button, and sends WM_CLOSE to the app, which can then handle it gracefully (or not) as it chooses.
In particular, if you have unsaved data, most apps will prompt to save on Alt+F4.
When Windows sends WM_CLOSE for any reason, it will wait for some time for the app to react (not necessarily close itself, just process the message). But if it does not react soon enough, Windows will mark the app as hanging, and you'll get that standard wait-or-close dialog.
However, Alt+F4 translating to WM_CLOSE is also handled by the app message loop - i.e. Windows sends WM_KEYDOWN events for those keys, and when they get to the event loop, it's supposed to call TranslateMessage. That one normally handles WM_KEYDOWN -> WM_CHAR translation, but it will also handle any shortcuts, and this includes Alt+F4. So if the app is hanging, messages aren't pumped, and the shortcut doesn't work. To send WM_CLOSE, you'd need to use the close button on the window.
So if the app does close on Alt+F4, it was, at the minimum, pumping messages and invoking TranslateMessage on them.
Well aware of that alternative :P I had a display glitch with a game client where it would take the whole screen but not really display anything, leaving me with sound and a working computer but no display even after alt+tab or even ctrl+alt+del. I basically had to blind type win+r > "cmd" > taskkill /f /im Gw2-64bit.exe whenever it happened :(
Alt-F4 makes little sense, true, but in almost all windows apps control-q or control-w does exactly the same thing as on osx.
Also, having sane defaults for keys people are likely to press is much more important than /not/ having obscure keyboard shortcuts that users never have to know even exist.