It does print a message, but doesn't prompt you for a response. I think that's the distinction that was being made.
Not in (my) vim you don't. You get:
> E37: No write since last change (add ! to override)
Yeah - I figured that was as close as Vim came to a prompt
It is prompting you to add a !
It has closer things to prompts. Try editing a file when the last time around you terminated vim without giving it a chance to clean up its .*.swp file. (-:
Actually you get a prompt when you try to save a file that has been modified in a different session or when you switch to a similarly modified buffer. But those are pretty reasonable and don't happen that often.