The packaging is pretty good, and IIRC there was a film over the glass, but not for structural support, only for protection against scratching or dust.
The glass is held on well enough for any normal handling. It is possible that since the glass is no longer completely surrounded by the frame, it can shift enough on heavy impact to break against it. The photo looks like that may be the case.
FWIW, the Apple packaging is the best I’ve ever seen for a computer.
I noticed that the spacing in the corner where failure occurred appeared to be much less than at the top. (IOW, the glass didn't look "square" in the case.) However, I figured that could be attributed to parallax in the photo.
Aside from "duct-taping" the glass around all sides for shipping, (or adding an adhesive bonding agent) I don't see how you could guarantee that big glass slab against heavy shocks.
Since I don't have a sample to work with -- or competitors to analyze, I guess my solution would be to label (in all appropriate languages) the packaging with:
"DANGER! NITROGLYCERINE -- DO NOT DROP OR JOLT PACKAGE!!!"
'-)