Output-Parameters in /history/detail

Hi,

im currently working on some custom frontends for displaying finished process instances (data accessed via REST-API).
Since I want to display value-changes and the task/activity where they were made, I encountered the problem, that for output-parameters the activityInstanceId is the processInstanceId. So I’m not able to link those to any specific activity.
Data from /history/detail:

11:
activityInstanceId: "Activity_1onp3ym:8cd1a312-e8f2-11ea-82cb-f875a4fd551d"
[...]
value: "input"
valueInfo: {}
variableInstanceId: "8cd1ca23-e8f2-11ea-82cb-f875a4fd551d"
variableName: "InputValue"
variableType: "String"
12:
activityInstanceId: "8cd106cb-e8f2-11ea-82cb-f875a4fd551d"
[...]
value: "output"
valueInfo: {}
variableInstanceId: "922e786d-e8f2-11ea-82cb-f875a4fd551d"
variableName: "OutputValue"
variableType: "String"

Is this intended, and why? Any suggestions how to link an output-parameter to it’s activity (time is no option since there might be parallel paths…)?

Greetings
KeyKon