Multi-Tenant Bounding Set?

[tshw]

Is anyone using the Tenant Bounding Set to allow user/group to access more than Content Store objects from multiple tenants?

It is my understanding that this is the feature to use if a user from Tenant A needs to access objects from tenants A, B, and C.
However the documentation gives an example of setting this value to a single departmentNumber value... which doesn't make sense to me.
IBM Support person seems to not know either, so if anyone has experience with this, please share?