RJ confirmed what I suspected from the antelope test - the DST was in a zone with low permeability and porosity.
Basically, what happened with the DST12 is that the tested zone had the gas/oil boundary somewhere in the middle. Therefore, since gas and lighter condensate flow easier than oil, they sourced mostly natural gas and condensate. DST13 was below the gas/oil boundary and they sourced only oil. The column is definitely thick enough for commercial production but the problem is that the oil is in the part of the reservoir where the rock is tight.
But in reefal areas like this, the rock quality can vary quite a bit over a few hundred feet. Possibly down dip, they would find good quality rock and a thicker oil column. The new boundary that they need to find is the oil/water boundary as that will be the limiting factor.
As far as different qualities of oil are concerned, it does not mean that the oil is from different sources although this is possible. What happens over time if there is sufficient heat is the oil "cooks" or refines in the rock. The larger oil molecules break into smaller pieces - some of which are various qualities of natural gas and condensate. How exactly it works is very dependent on the chemistry of the oil and the temperature and age of the reservoir. So, in another 10 million years, the 35 degree API oil that they find now might have converted mostly to natural gas and condensate. Eventually (few tens of millions of years), the condensate would convert to natural gas and the larger molecules of natural gas would convert to lighter molecules. The gas would become dry gas with very little oil and condensate.