Most agile frameworks, especially Scrum, are very light and tend not to focus on project delivery (favouring instead a very lightweight approach to product delivery). This isn’t a problem in many environments, but where a project involves governance processes (in regulated environments for example), complex dependency arrangements, multiple vendors, offshore locations etc, you need something that offers a little more structure.
Prince2 Agile focuses on agility at the delivery level (Scrum, Kanban, etc etc), whilst still enabling/facilitating project type controls at high management levels - thereby ensuring a delivery that regularly tests a business case and stays within compliance.
Standard Prince2 tends to ignore actual delivery, so has often been used in a very heavyweight way - the new course tries to fix that deficiency, and broadly does that well.