It may well be reinterpretation of perfectly good, but different, settings from previous version doing different things during update.
I'm wary of those kind of things, and that's why I never update my linux box but just reinstall and keep my /home intact.
Even doing so, from time to time I have to wrestle some kde inconsistency due to the same config files in my home being converted to the new release, and not producing sane results.
My guess is: who used their macs more or less to the defaults are fine. Those who prefer to tweak many settings will have more chance of getting this behaviour.
Of course, I don't have a mac so this is all pure speculation!
Isn't it possible to reinstall everything and keep just the home directory?