About plugged and unplugged

[Harry Putnam]

When is `unplugged' not really `unplugged'

I must not really understand what plugged and unplugged really mean.

For example I can go unplugged in group buffer.

Then enter a group (gmane.comp.version-control.git.user) with the
command
C-u 12000 <ENTER>

When the group opens I actually have 11383 messages and I can open and
read any of them.

However in
 /News/agent/nntp/news.gmane.org/gmane/comp/version-control/git/user

I only have 6049 messages on disk

ls
~/News/agent/nntp/news.gmane.org/gmane/comp/\
     version-control/git/user|wc -l

6049

So how is it that while unplugged, I can open thousands of messages I
do not have on disc?  That is confusing.