You're right
ned, flavouring is more than one ingredient, so 4 is basically untrue.
The thing with Diacetyl is that it shouldn't be in eliquids, its most commonly found in buttery/creamy type liquids. it's a risk that is known and is avoidable, as it potentially can lead to 'popcorn lung'.
However , the reason why vaping is so much safer than smoking is that there is no combustion. It is at combustion point that the vast majority of toxins are released
Things are very different today than when smoking was found to be bad for us in the 1950s. We have huge amounts of information about what chemicals cause cancer, and importantly the concentration.
Nothing, repeat nothing has been found yet that is sufficient to think vaping will cause cancer. We can never say never but Professors with 20 years experience in tobacco harm reduction estimate that it's about 95% less risky than smoking.