Personally I don't know, but it might have to do with what VPS version is contained within the installation file. File hippo is somewhat different to most as they are also keeping older versions and even the latest version may have an out of date VPS.
I also tend to use the download directly from avast.com, a) you are getting it directly from avast, b) that is frequently a faster download direct from avast.com as the others being major download sites are often busy.