You are right, it is not a website, at least not a real one.

What I was trying to do is what is explained in this HTTracks FAQ:
<http://www.httrack.com/html/faq.html#QM11c>

I was trying to "mirror" a local photo album written in html. The mirror will
be put on a usbdisk and then given to family or friends. They can then use
their browser to look at the photo album.

Creating a copy works as expected: only the needed files (the ones linked in
the html pages) were copied. But updating it will rewrite all files, even
files that haven't been changed... and writing to an usbdisk can take a long
time.