There is a current (pre-dated the event) FSO about the requirements for turning onto a parking bay. Basically
- NIGS (that states correct A/C) or a marshaller
- equipment is behind the lines
- green light on the bridge (as applicable)
If these aren’t satisfied then you’re not supposed to turn onto the lead in line.
In Perth we are always received by a QF engineer so I would be amazed if a contractor was directing the aircraft if they were following a marshaller.