Quick reply...
I am trying to figure it out now, too. You can send a email to Xavier, the developer. So far, I haven't noticed any difference, either...
Ah, here is it! [I caught the fox's tail]. It's a plugin adding a menu entry in Contact's view to display the vCard with bigger font, making it much more readable.
Open addressbook.
Click a contact.
Click the titlebar.
In the menu, there will be "Contact zoom".
Simple, and yet too far away to be of use, much of the time.
Best wishes.
_________________
Per aspera ad astra...