You're totally right, I spoke before I tested <smacks self>.

It's easy enough to see if you just do something like:

perl -e 'system("sleep 10")'
[download]

which returns imediately. I must have been thinking about something else. (Particularly, I think I was thinking of some recent question in which someone wanted the exit status of the backgrounded process... and that's not at all the same issue... oh, well)