Why is git-clone --reference so slow?

My DSL line sucks; I know this. But why is git-clone so bad at using it?

This is slow and seems to be downloading a lot of stuff it doesn't need...

pmac /pmac/git $ git-clone --reference /pmac/git/linux-2.6 git://git.kernel.org/pub/scm/linux/kernel/git/geoff/ps3-linux.git
remote: Generating pack...
remote: Done counting 14428 objects.
remote: Deltifying 14428 objects.
remote:  100% (14428/14428) done
Indexing 14428 objects.
  25% (3662/14428) done

At this point I got bored and hit ^C, then logged in to hera and did it there, then rsync'd the result...

hera /home/dwmw2/x $ git-clone -n --bare --reference /pub/scm/linux/kernel/git/torvalds/linux-2.6.git /pub/scm/linux/kernel/git/geoff/ps3-linux.git 
remote: Generating pack...
remote: Done counting 14490 objects.
remote: Deltifying 14490 objects.
remote:  100% (14490/14490) done
Indexing 14490 objects.
remote: Total 14490, written 14490 (delta 579), reused 5598 (delta 367)
 100% (14490/14490) done
Resolving 579 deltas.
 100% (579/579) done

pmac /pmac/git/ps3-linux $ rsync -avz master.kernel.org:/home/dwmw2/x/ps3-linux/ .git pmac /pmac/git/ps3-linux $ echo /pmac/git/linux-2.6/.git/objects > .git/objects/info/alternates

That was a _lot_ faster, and abused my poor DSL line a lot less. Why's git so bad at it?