The heat image, a couple of minutes out of the water, will most likely show the average heat along the center axis as the heat in the middle will conduct to the outside, so it will be a 'blurred' image. I don't want to conclude too much from it.
The video you linked shows the heat intensity - *not* the co2. If you take a look at one of his other video's he shows the simulated absorbtion reaction. This video shows that the actual breakthrough will be along the colder walls - not in the middle. So, yes, the CO2-front will form a cone, however it is a inverted one with the CO2 along the walls leading and the center lagging.