On the new System directed cluster picking a cluster will not be created if there is not enough work to fill all the slots in the cluster, but it will create a partial cluster after a full cluster is picked. For example I created a Mobile device menu item linked to a 3 slot Cluster profile. When I created work for a single Sales order and tried to use the menu item it showed an "Insufficient work" error. When I released 4 Sales orders it created an initial cluster of 3 works and then a second cluster with one work.

There will be times when you want to pick a partial cluster and times when you won't, so I propose that anytime where there is less work than the number of slots there should be a prompt to saying something like "There are x works and y slots, do you wish to proceed?"