Most PMOs, if not all PMOs, are reliant on a stage-gate process (which has also been known as a phase-gate process) to govern their projects. This makes a lot of sense because it's simply too risky to give all the money to a project right at the start of its development.
Instead, it's much more logical and sensible to ration and release funding in tranches, aligned with the project's natural life cycle. This enables the PMO to effectively govern each project, in a controlled and consistent manner, based on its outputs and value delivered to the organization.
There are numerous and various stage-gate processes out there, even within the software project business. A lot of organizations have developed their own models to suit their context and needs, which is perfectly sensible and reasonable.
As we discussed in Chapter 4, A Week in the Life...