I recently tested which rights a "Privileged role administrator" because it's the only role (except Global Administrator) which gives access to managing Administrative units in Azure AD. When testing these rights I noticed that a "Privileged role administrator" has the ability to manage assignment of all Azure AD roles up to and including "Global administrator", something which in my opinion partially defeats the purpose of the role as it makes it quite simple to circumvent the limitations in place and gain Global administrator oneself.