In some cases the issue that you can't really "blind" it because it is a physical continuation of the earlier work - not just building upon the idea, which anyo

In some cases the issue that you can't really "blind" it because it is a physical continuation of the earlier work - not just building upon the idea, which anyone could do, but using the exact same experimental device (a unique one, like the hadron collider) or continued analysis of the exact same set of patients or animals, or improving the previously made software tool.