A thing I think I'm seeing is that #ProductManagement has been so poorly practiced that #design #ProgramManagers have had to learn the basics of the role (discovery, requirements, roadmap, prioritization, backlog management), which means that
a) they're no longer doing the core work of #ProgramManagement
b) as product managers learn their role, they'll bump up against DPMs.
Program Managers may resist a focus on core program management, as it could feel like a loss of influence.