As far as I know no one has died, either directly or indirectly, from smoking pot, unless there may have been a chronic condition. The professionals you listed above only rely on what the Govt. feeds them, in this case in Canada. I have done quite a bit of studying cannabis.
My opinion, somewhat backed up by these "professionals", is that anyone under 18 to 20 years old shoud not smoke pot, the brain is still developing and you don't want to disturb that process.