niniendowarrior: I'm pretty sure ELF binaries don't run on Windows. LOL
I was personally wondering whether Steam packages both executables into their releases since most of these cross platform games share the same assets. It felt like a streamlined approach to me, but probably isn't going to work.
LOL ^_^
I use the Backup/Restore myself, and I have found many instances were just changing the language of a game, Steam starts downloading the audio files that are missing, or need to be changed. So I think that Steam only downloads the minimun necessary, instead of everything, probably to save bandwidth.
Maybe as you say, different versions share exactly the same files (same CRC), so there's that possibility that you can save some bandwidth restoring a previous backup from a different version, and Steam will only download what's missing...