Most secure way to find out all references is a combination of both. You also have to make sure indexing is proper not to miss out any rule while searching.
Rule references are created when one rule refer other in a model driven way (Property-Set etc. ). They are stored in each rule. In your example, if you open XML for your data page referred in the screenshot, you will find a pxRuleReferences page which contains all rules that this data page refers. Similarly, other rules which use this data page will have an entry in their pxRuleReferences.
Note: Using or calling rules directly in java steps will not make an entry in pxRuleReferences and hence will not come in View References window.