These two terms are lumped together because they are the same concept, seen from opposite perspectives. You can disaggregate an area into a number of patches; or you can think in terms of one patch, then have multiple patches to represent some larger area. The end result in both cases is exactly the same.
Once you have made a submodel you can specify (in its properties dialogue box) that it is a “fixed-membership submodel”, and specify a number of instances. The submodel then represents each of that number of instances. Visually, it now appears different, because it now has multiple lines on the left and bottom edges (rather like a stack of cards). Internally, Simile now handles each instance separately: each can have its own parameter and initial values, while they all have the same compartments, flows etc.
This enables many forms of disaggregation to be captured. For example: