I believe it’s both really. My understanding is the end caps are bolted to a titanium flange, not the carbon fibre hull directly. The titanium flange the caps are bolted to is epoxied to the hull.
Yea, you generally try to avoid drilling holes or even casting threaded bosses into carbon or other composites, especially this extreme pressure rig, because it really reduces the strength versus an strong adhesive that evenly applies pressure without breaking/disrupting the composite material.