I think the major focus is on performance. There was an issue that some servers where haveing with freezing every x amount of mins for a few seconds and I know WH has been actively trying to improve things so that does not happen. I would imagine if they did give details on what was being done each time that the majority of use would be totally clueless on what they have said. :)
I belive that also any time that an update of something needs to be done that they have to make some changes. They have been working on upgradeing perl and some of the other basics so some of the maintnance could be in preperation for that.
As Armadillo said... "Upgrades are good. Usually."