Professional traffic controllers do not need an additional certificate as stated in the BRL9101. You can read below where this comes from.
The Stichting Infra Kwaliteit manages the exams for the installation of traffic measures (the KOMO BRL9101 certificate). This means that companies involved in the installation of traffic measures must have a BRL9101 certificate under certain circumstances on behalf of a number of road authorities such as Rijkswaterstaat.
Employees working for these companies who are involved in working within these road closures and placing these traffic measures must be in possession of the personal certificate BRL9101.
This working group has now decided that traffic controllers working within this sector and criteria must also obtain a person certificate BRL9101 for traffic controllers. Practically, this means that these traffic controllers apply for a VCA, BRL9101-VKM and after a successful traffic controller exam under the supervision of the police, apply for an appointment and then obtain a BRL9101-VKR certificate to be deployed as a professional traffic controller for traffic measures under the BRL9101.
In order to be able to be deployed as a professional traffic controller on various roads, ONLY the professional traffic controller exam via SVNL and an appointment by Rijkswaterstaat or the municipality is required. The Regeling Verkeersregelaars is clear about this. A BRL9101 certificate is not required for professional traffic controllers, except for the activities referred to under BRL9101.