"Don't know why shallow water and deep water drilling and the DST test thing are not treated the same"

Generally shallow water drilling can use jackups, which are much cheaper than the drillships that are used in deepwater. The high dayrate for drillships is probably the driver for dispensing with DSTs in deepwater.

Unfortunately GKG-19 & 20-ss are caught in the middle. Too deep for jackups, but not considered deepwater. A solution would be to require DSTs for onland and jackup wells, but excuse semi-sub and drillship drilled wells.