I think it's to do with the bottleneck shifting away from code generation and towards specifying and reviewing and integrating code. The process of working with AI agents to produce specs, tech specs, code, and reviews lends itself more to a flow-based structure (like kanban).
Bear in mind this is a B2B enterprise company with a mix of legacy and greenfield. And management has invested heavily into designing a robust spec/context-based workflow for using agents. Might be different elsewhere.
Personally I don't think scrums, planning, retros etc were better than kanban even before AI, at least if you have switched-on, motivated and smart people on your team. They actually made things less agile, and story-points give a false sense of predictability. Imo the crucial factor may be that AI agents are smart and switched-on (with the right context).