I have to moderate card sorting session. Our team wants to reorganize navigation in account of financial company's client where he can see information about products and services he uses, conduct payments and transfers, and get new products and services. There is a request from product owner to reduce the number of groups if there will be too many of them.
Should I ask the participant to reduce the number of groups during the session if there are more than maximum I have determined? When exactly should I ask him about it? What if he can't because there are no more groups that can be joined to his opinion?