I’d argue that “far fewer” is not that much of a science. How much less of each exactly? How does the smaller amount affect cancer and other diseases? (linearly? sublinearly? no long-term effect from this reduction in dose? Higher cancer risk because of the vapor?)
How smokers’ habits change with vaping? Do they vape more often than they had smoked? Is vaping more social, hence more people get “sucked in”? Do children start vaping earlier? Long term, is starting vaping better than trying to stop smoking?
So many facets, so much beyond “we found this number smaller, therefore we recommend smokers to vape now”
It’s a “vaping has far fewer toxic chemicals compared to cigarette smoke” type science.