Earlier quoted context omitted.
It's not just about the weight on the plane. It's about the equipment and people who move the bags around. Clearly, people have some upper limit they need to be expected to lift as baggage handlers.
It was a carry-on bag that was overweight, so nobody other than the passenger would be handling it.
You can see out the window of the plane the way handlers drag and drop even much lighter bags and crates, even when tagged “fragile”, how much the weight matters and how much they give a s. I have video. The jars survived. Double-boxing ftw.