Spell Casting
Spell Casting (p.100) 
| The PHB’s spell casting section — covering interruption, concentration, components, and the procedural mechanics of casting a spell in combat — is superseded in Oath-Bound. The procedures described assume the memorisation and slot model, which does not apply. |
The underlying concerns the PHB is addressing — can a working be interrupted, what happens when a caster takes damage while working, what physical or vocal actions does casting require — are real questions that Oath-Bound also addresses. The answers are different.
For Arcane Actors, working through nwyf requires concentration and is subject to disruption. The specific mechanics are governed by the CRM arcane rules rather than the PHB’s segment-based interruption model.
For Divine Actors, the situation is different in character. A divine mandate is not a procedure that can be interrupted in the same way an arcane working can. The GM adjudicates disruption of divine action on the basis of the specific circumstances and the nature of the mandate being executed.