I think the verb tenses were not perfect... I think he just meant: why did they build only 1 in the first place? They could have built N instead, at a lower cost per unit.
If it fails, they'll learn all they can, then try again with another follow on project, that likely will take advantage of technological improvements since functional requirements on this one were set in stone. Pre-building a spare just doesn't make sense with this kind of project.