Love the term "value engineering!" We used to have to do those studies, usually to figure out what crazy alternatives we might have to deal with during public review, or sometimes to justify that what had already been approved could withstand late-hit crazies. It was a checklist item for FHWA.

Rarely, it would happen because, as is apparently the case here, it was realized too late in the process that there wasn't enough money to build what was wanted, but there might be enough to build something while leaving stubs for somebody to hook up to in the future. That last situation was usually considered a failure of project management, especially because it would cause further delay while environmental documents were modified and (sometimes) run through another round of public review. So the Metro people here are certainly guilty of that.

Note: NEPA was actually completed a long time ago, along with CEQA, for the project. It was reopened to deal with an apparently late add-on of work around Malabar Yard to make up for loss of BNSF yard tracks where the run-through tracks come back to ground level. Why that wasn't noticed up front...?