Duan Gauche, Value Stream is also a Thing with Parent as Value Stream Thing Template but we do not have access to the Value Stream entries from the Value Stream Thing. The Services for Value Stream are accessible only via Things using that Value Stream Thing.
So, as Polina mentioned; we need to run the service PurgeAllPropertyHistory, PurgePropertyHistory, PurgeSelectedPropertyHistory from the Thing using the ValueStream Thing i.e. The Things where the Value Stream Property is set as our Value Stream Thing.
If you are running the Service from the Thing using the ValueStream and it still does not work; I would suggest you to check Script/Application logs if it shows any error.
When you call service PurgeAllPropertyHistory to remove all the data entried from a Thing using the Value Stream, make sure you also select the startDate and endDate, and also make sure the startDate is on the bottom and endDate is on the top, please not choose it wrongly and then execute it to see if data entries could be removed.