Unless it's a heuristics or rootkit detection (both of which are somewhat rare, or let's just say less common), you don't submit the actual sample, just the bit of information that the virus was detected.
This allows us to build charts like this
http://www.avast.com/virus-monitor and also helps the virus lab to prioritize samples (which is very important).
But to answer the original question, I'm not sure actually. In v4.8, it was like DavidR described, but I'm not sure about v5. But I generally agree it should behave like this, so if it doesn't, I'll file a bug and it will be fixed in an upcoming program update.
Thanks
Vlk