There is no any difference. It is the same and was posted if someone need to do reflash of the box.
If its the same as on HIMEDIA support page , then why bother remame it ?
We've always name our HiMedia firmware like that, since a long time before HiMedia had their own download site.
By packaging the update.zip file inside an archive it avoids the possibility of a corrupt update.zip. It also allows us to package a readme.txt file.