Some users may have incorrect phasing assigned to features from CAD imports, redundancy, or other causes. Examples include a single phase linear feature that has an ABC phase designation, or 3-phase transformers that only have one-phase loadpoints downstream.
Responder has changed, starting at 10.0.2, incrementally over several versions, to work on only the phases reported out. It ignores any other phases it encounters on the traces. For an A-phase outage example: When we create the outage we do an upstream trace and only resolve a path on A, then when we create the loadpoint we only take it out on that phase, to restore that loadpoint we only need to restore on A-phase.
We recommend users run the Responder Data Validation tool. This tool will find many of these scenarios and provide a report of its findings for your data corrections.