Yes, they had some reserves even OTL, and part of them were committed to Stonne and other places, some of them got chewed up by the advancing German panzer formations etc. etc.
This is not about that. This is about not implementing the 'Breda variant' to the OTL 'Dyle Plan', meaning that the 7th Army (one of France's best formations), remains part of the strategic reserve and is kept in place north of Reims, a stone's throw away from Sedan. This would put them in an excellent position to be deployed against the German Schwerpunkt when they try to cross the Meuse and consolidate their bridgehead.
Given the French command structure, they are liable to screw it up anyway by dithering for too long. Would they though? Or do they have a chance to make this work?