It does not say whether there was any airflow past the coil in that test. In any case, 300C is way too high, since that would instantly carbonize glycerine, which obviously doesn't routinely happen in our use of these
devices...
Occasionally, atomizer
coils pop (melt). In the case of Kanthal, the coil temperature must have reached about 1200C, 1473K, 2190F.
When an
ecig is used, sometimes there is no airflow over the coil. Sometimes the coil is energized before the user begins to puff, and the coil remains energized after the puffing has finished. Sometimes a user makes multiple puffs while the coil is energized, and in between puffs there is no airflow.
I would not be surprised if an analysis of coil gunk showed it contained carbonized glycerine. I would be very surprised [if] it did not.
I'm starting to think it might be less risky to vape a thin mix containing little or no VG, at the lowest wattage. Perhaps even a thin mix of PG and water. I'm going to give it a try. I don't expect it will be very satisfying though.