Just a guess here but maybe the Carbon versions of some of the apps are inherently larger than their Cocoa counterparts.
Any thoughts on the decrease of app sizes? Most of the size currently comes from the resources that come along with the app instead of the binary itself (nibs, localization, images)
Did they reorganize this to reduce duplication of files or change the format of bigger files... or just not include localizations you don't need?
My understanding is that the apps have both compiled version in one .app file. The resources files are used by both... The size reduction comes from not having Carbon versions included in the .app file (and presumably Carbon binary blobs are bigger than their Cocoa brethren)
PPC no longer being supported means this could happen.