I don't know if two are the same, just that some elements of the update aren't used by 4.8, so I quess those could be stripped out, so after testing they could be released to both at the same time. Though if you do a manual download of the full VPS there is a difference,
http://www.avast.com/download-update. There is quite a big difference in size too, with 4.8 at 32MB and 5.0 at 28MB, so it looks like the 5.0 VPS is more efficient, perhaps due the the new algorithmic, heuristic signatures.
That has already been reported and acknowledged and they will get on to it. As you might imagine the complete revamp of the web site to come in line with avast 5.0 release must have been a huge task. I'm sure this isn't the only thing needing attention on the new site, so I guess we will have to await its update in line with their other priorities.
Whilst the new page is there it doesn't yet include the 2010 updates.