Well, information on how to migitate the cancer risk is already a step forward.
If it is only harmful if ingested you know not to give it to your toddler. If it gives off toxic fumes while burning, well, stay away if you made a fire mistake. etc. The warning itself is pretty useless as it is.
We have to find a middle ground between "has chemicals that may cause cancer" and "a hundred specific chemicals in X quantities that may cause cancer." Abstraction is very necessary as a pragmatic solution, even if full disclosure makes sense as an ideal.
Heck, most places are just doing CYA, they have no idea what specific lists of chemicals their contractors use. For the IoT case, no one has any idea how their devices can be exploited, and merely admit the possibility of exploitation. But that is another issue.