Each of these services solves a different problem, but the reason to keep them with the same vendor that molds the part is the same across all three: fewer handoffs.
A part that ships to a separate finishing house, a separate labeling supplier, or a separate assembly shop gets re-inspected, re-queued, and re-explained at every stop — and any tolerance or fit issue that shows up along the way has to be traced back to a vendor that isn't the one who can actually fix the mold or process.
Coordinated planning establishes who is responsible for each operation, which approved specification applies and how parts will be inspected before transfer or delivery. Production locations and handoffs are reviewed for the project.