This area has been declared as 'fietszone' (fietsstraten the moment it was announced by the local council (Oct 14th, 2020). It concerns the area surrrounded by the Weststraat, Sint-Pietersstraat, Hoogstraat and Stantionsstraat and includes the Markstraat, Kapellestraat, the Le Marais Vernierplein as welll as the Sint-Pietersstraat.
A full declaration can be found on their site under 'verkeersreglementen'. At the moment of this writing it is however not possible to modify any attributes on OSM as the signage in place does not really reflect the description as found in the official document (oct 2020)
I suggest to monitor the situation and only further modify any attibutes when the signage is made consistent with what was decided in 2020.