General Issue: Nodes that take two Nodes as inputs work only on two nodes. Not 1 node, not 3 nodes, two nodes. The UI for linking nodes is not similarly constrained. I found this out because my model (for Oathsworn: Into the Deepwood see here) uses a pool of any number of dice from any combination of 4 different custom dice pools.
In my model, I not only need to merge 4 pools, but I need to generate a "Fail/Miss" outcome when 2 or more dice in the merged pool come up 0. I thought a Switch Pool would work, but I had to create a dice pool that always generated a 0 result because the Switch wouldn't work without a 2nd pool input. I had thought I'd be OK because I use the output of several of the model's nodes as input to multiple other nodes. It turns out that multiple outgoing links from a connection point are not handled the same way as multiple incoming links to a connection point. It makes sense, now I understand the model, but the UI isn't constrained to fit that model.