If the target operating model states the intent, the blueprint provides the detail. It takes each element of the model down to a level where it can guide real design and delivery decisions, connecting the layers so they stay consistent.
A blueprint is more than a set of diagrams. Its value lies in the links between elements — a process tied to the capability it realizes, tied to the role that owns it, tied to the technology that supports it — so change in one place surfaces its effect elsewhere.
It serves as a shared reference across a transformation. Programs, teams, and vendors work from the same specification, which reduces the drift that occurs when each group interprets the target differently.