The fact of the matter is that the sedimentary rocks in the Gulf of Mexico extend far deeper than 6,000 below the sea bottom where the reservoir was initially tapped. The area is heavily faulted. Whether through pressure depletion of the shallow producing formation as the first wells were drilled, or through some lower techtonic event, oil in a deeper, untested zone migrated up past a previous seal (probably along a fault line) and replenished the reservoir.
All that Eugene Island 330 proves is that the industry hasn't drilled deep enough in the Gulf to find oil currently trapped in place.
Your observations, however astute, do not address this situation.