Quote - I understand that the add-ons using exp basically add new morph channels so that they do not have to be pre-defined. So a morph package add-on needs to hack the cr2.

But why does the base V4, without any add-ons, need hacking?

Technically there is no reason that I can see why DAZ should require this for the base V4 without any add-ons. Perhaps it's just laziness on the part of DAZ. Personally I prefer to take a kinder view. Perhaps DAZ just wants to get us used to using the updater, so it does not come as a surprise when we purchase new content.

Strictly speaking the updater does not "hack the cr2". Let's take V4 as an example. The cr2 contains two readScript lines for each actor. One line points to a pz2 that contains a list (as readScript calls) of all channel groups for that actor, and the other line to a pz2 that contains a list of all the channels for that actor. These first level pz2 files are in the "libraries!DAZVictoria 4 folder. The the updater bat (eg "DzCreateExPFiles-V4.bat") starts a process that writes these first level pz2 files on the basis of what second level pz2 files are available in the  sub-folders of the Victoria 4 folder.

Any rate dkal, that's also the answer to your original post. The initialization is there so V4 can use add-on packages (that use ExP technology) without the need to to apply the packages each time you load V4.

By the way, Cage has a script "morph_slot_maker1g.py" that can add new targetGeom (morph) channels to a figure in Poser. You select the figure, run nthe script, select the pz2, and the script adds any missing channels to the figure. In my opinion this is a superior method to both ExP and PMD technologies.