OJ-SELECT-SINGLE equivalent for detail.trigger == "option_selected"

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We are in process of migrating from OJ-SELECT-ONE to OJ-SELECT-SINGLE.
One of the main filters that we have in any value change actions in Select One is detail.trigger == "option_selected"
This is in order to execute the actions only when the value change is triggered by a Drop Down Selection, not any value assignments.
What is the equivalent for the same in Select Single? I could not see the trigger property in the event's detail for Select Single.