I don’t know if it’s expected, but if you hit CMD+S while in Preview, RW7 asks to save web page, not project file.
But, you are in the browser, right? I would expect this behaviour 
I’m not in a browser. I’m in a embedded webkit window with no navigation toolbar inside RapidWeaver.
Doesn’t happen for me…
After a restart, it doesn’t happen to me either.
I’ll try to find a way to reproduce it.
Never seen this myself. As far as I’m aware only Safari saves webarchive files. I’ve never seen RW do this. I didn’t know that was a thing it could do.
When you open Web Inspector the focus goes to the webkit page and hitting CMD+S the window above appears.
But when I reported the problem, inspector wasn’t open, so I guess that some “clicking and switching” while I was editing my project changed the focus someway.
I’ve managed to replicate this when the Web Inspector has focus. I’ll add it to our issue tracker and see if we can get it fixed. Thanks for reporting it!