What is the reason for DCS?
If the diver surfaces too quickly, however, potentially dangerous nitrogen bubbles can form in the tissues and cause DCS. These bubbles can compress nerves, obstruct arteries, veins,
The reason that all DCs are not GCs to start is that in large (or even Giant) forests the DCs would all have to hold a reference to every object in the entire forest which could be quite large and quite a replication burden. For a few hundred, or a few thousand users even, this not likely to matter unless you have really poor WAN lines.