I summarise Agile leadership like this: “Stop giving solutions to people. Give them clear outcomes to aspire to. Give them enough space and support. They will figure it out.”
Nothing Earth-shattering. It’s no different to the military’s age-old “Commander’s Intent.”
Most portfolio management schemes I’ve encountered are top-down management, coordination, and progress-tracking work. More mature ones have prioritisation, WIP-limits, and with strategic underpinnings in there as well. And a lot of them probably work well in their context.