The story which I heard a few years ago (when win98 was still new) was that a bug in the windows clients prevented them from showing shares ending in a $.
Not just administrative shares, any shares.
Later this got changed into 'not a bug. A feature'. Or 'all windows clients will hide shares whose name end with a
$. Not that this is done at the clients. Not at the sharing side. Thus they are not truly hidden at all. They are merely not shown (by default) on windows clients.
As with all things, take the old story with a grain of salt. The only reason why I believe it might be true is that no sane person would implement the security/hiding at the client side.