I don't know if it's been mentioned before but, from The Verge-
"The video itself may have seemed like an innocent hands-on, but it did include footage of an iPhone X with special employee-only QR codes. A notes app was also shown on the iPhone X in the video, which appeared to include codenames of unreleased Apple products. Filming on Apple’s campus is strictly prohibited, so filming an unreleased iPhone X is a definite rule violation." (emphasis mine)
This wasn't just "I showed off my dad's iPhone X and now he's fired". If they just let it go because it was someone who had no idea what she was doing then next year when some employee let's his sibling see the iPhone 10.1 (Puma) and argues that, "hey, it was just my brother ok? How was he supposed to know not to blab about it on his Tumblr?" how could they lay down the hammer when they didn't in this earlier case?
You can't stay two to five years ahead of the competition if you've got a bunch of knot-heads that can't keep things under wraps. Loose lips sink ships.