What label would you use for it? I’m not trying to be disingenuous. Big Design Up Front?

Eh, does everything need a label? Just prototype an iterate on the core things u need to do in your game as early as possible, with just one programmer if possible. Try and decide those big decisions like, what engine to use, and test that your choice will adequately handle the important things u need for the project. Before hiring a tonne of people and spamming code and assets everywhere.