The number that justifies this role
A clash found in the model costs about an hour of your time. The same clash found after installation costs a fortnight, once you count demolition, re-fabrication, re-inspection and the trades queued behind it.
On a mid-size build we see 900 to 1,400 genuine clashes. Moving resolution from 95% to 99% is the difference between roughly 50 site-found clashes and 10 — about 80 days of disruption. That is the whole business case for this job, and it is why the role reports to the technical director rather than sitting inside a drafting team.
The hard part
Getting to 99% has very little to do with software. It is three unglamorous disciplines: model quality from subcontractors, tolerance rules that distinguish a hanger brushing a conduit from a fire damper missing its opening, and actually closing the register.
You will spend more time managing people’s model hygiene than modelling.
What coordination does not catch
Sequence. A model can be perfectly clash-free and still describe a building you cannot construct in the order you planned, because the crane cannot reach or the room cannot be closed until something inside it is commissioned.
You will run a separate constructability review for exactly this, with site staff in the room. It finds a different class of problem.