Nothing new here. Since the first samples were brought back on Apollo 11 they've knows that if you cook the stuff it will liberate the oxygen.The particles would then be blown into a reactor with hydrogen and heated to 2,000 degrees Fahrenheit. At this time, the oxygen released from the oxides would attach to the hydrogen and be collected.
It's just basic science. Take a real copper penny and hold it in a burner flame - when it flashes back to the light copper color (like a new penny) it's because the oxygen has flashed out of the oxide on the surface. Different oxides decompose at different temperatures, that's all.