Linux and patch policy
"Have you tried explaining to her that Linux allows her to do a bunch of stuff the average user has absolutely no interest in while losing highly desired abilities?"
Not really, because the people I usually talk to want to use a web browser, play facebook games (flash), mount usb sticks, and play videos... maybe light word processing, pulling photos off their phone or camera and sometimes printing an scanning.
Anyway.. as for the policy of not describing these cumulative updates, I'm guessing there are just so many changes throughout the system that it wouldn't be useful to enumerate them all. I mean, when I had a VM with Ubuntu 14.04 on it a few months before release (like February or March or so), each and every update was listed in update manager, but there were like 100 a week so it was honestly not that useful.