There are two different spices that we call 'cinnamon': ceylon and cassia. From looking at the review you've linked, it appears they mean cassia. Cassia (also called 'Vietnamese') tastes quite different from ceylon (also called 'true cinnamon). You have to go out of your way to get the cassia, so if the studies are all with cassia, then that's what people will find in the supermarket (and coffee shop).
Mentioning this as the first cinnamon photo is ceylon, the second is cassia...