Climbing is completely prohibited
The area is basically closed since 2020 because of a nature protection program (IBR). The Integral biological reserves are protected natural areas without human intervention. It's forbidden to go over any fences or leave any marked paths and you might get fined doing so. It's not basically forbidden to climb, but because climbing would mean in most cases leaving the trails, one can say climbing is forbidden.
Instructions to get there if area opens up again:
Park as shown and walk with Route d'acheres a Arbonne to the sectors:
Turn left to Route des platieres if you want to check out the western parts.
Otherwise continue for 200m more and turn right and walk 200m more to get to the main area.
The northern part are just above Route du Furet, most of the boulders visible or barely visible from the path.