Confused by restore(8) man page example

[Ronald F. Guilmette]

In the man page for restore(8) I see the following:

    The -r flag ... can be detrimental to one's health if
    not used carefully (not to mention the disk).  An example:

             newfs /dev/da0s1a
             mount /dev/da0s1a /mnt
             cd /mnt

             restore rf /dev/sa0


Personally, I utterly fail to see what point the author is attempting
to illustrate with the above example.  I mean what part of this, exactly,
may be "detrimental to one's health" ?  It's an enigma to me.

All I see is a pre-existing BSD partition being explicitly newfs'ed and
then mounted, followed by some stuff being restored to that (clean)
BSD partition from whatever is currently sitting on the tape drive
called /dev/sa0.

So?  What possible problem could derive from merely that?  I don't see
any.

What's the problem?  I'm confused.