It stores meta-information about the files in a xml-file, including the sha1sum of the files. This means that if you move, reogranize or rename your files, the meta-information will still apply.
The meta-information -also- sticks if you edit the file, because it has filename AND sha1sum. But if you do both, you lose the meta-information, unless you run "update sha1sums" (a maintenance-tool available in the tool-menu)
So "edit + update sums + move" is fine. But "edit + move" results in lost metainformation. Reasonable, in my opinion, because if the FILE changed AND the filename changed, how is any tool supposed to know it's "the same" file?
Kphotoalbum also does NOT import your pictures, nor ever change them in any way (though it supports kipi-plugins, and some of those do modify files)