Yes, exactly. You got it on the second guess. Thing is, browsers
can't fake the warm fuzzies -- they can only wait. But the server
often can give a progress indicator. It can say "I'm half-way
through all the files". Telnet-based Archie servers do this today,
gopher servers tend to manage it because clients display data
as soon as they get it. WWW can't do this -- your only comfort
that anything is happening is Mosaics spinning globe. That
makes for a lousy interface.
You may not think warm fuzzies are as important as, say, whitespace,
but I sure think a mechanism like this would let HTTP server
admins provide an even better service.
You seem to worry an awful lot about effort when there's no effort involved
here. It all fits nicely and NOBODY has to write any code unless
they want to. They just need agree that the mechanism would be nice
to have.