For the rest of us, this is expected behaviour, and I don't want 7z special-casing exes or always extracting all files in an archive just to open one.
This seems the expected and reasonable behavior to me, as a second data point.
7zip is good for extracting archives somewhere and for supporting a ton of archive formats (and especially for supporting disk image formats!) but as an archiving tool its features are barely barebones.
Which is basically why on Windows i tend to have both installed - WinRAR for being an actually good (and very fast) archiving tool and 7zip for handling the archives WinRAR cannot handle.
(though nowadays i handle most archives via Total Commander - which i use even on Linux via Wine :-P - which asks you if you want to either extract just a single file or all files in the archive and is IMO the best approach anyway)