"problem" is a bit of a strong word, but when someone says "Cancer Death Rate Dropped" dropping people assume "Cancer Rate Dropped", which is not at all the same thing

The article provides no numbers about cancer rate dropping. Yet the false association between the two ideas is so strong that even the authors themselves seem to theorize that the cancer rate itself is dropping because people don't smoke as often now.

Conflating those two concepts seems like a Very Bad Idea