I don't think there is a current workaround for this issue. May ask exactly what is attempting to be accomplished with displaying when the extract finish time? In theory anything in the extract at the start of the refresh will be in the extract when done being created. If you displayed when the extract finished, there might be discrepancies between the actual data captured by this extract and the captured 'Data Update Time' time shown on the viz.
**For example if it takes 30 seconds to load the extract and the time was displayed as 01:30:25 as the completed refresh time when the extract was started at 1:29:55 then any data that was added to the data source would be 'basically' lost in this time lag (of course the data is there, but it will not align with the update time listed as the data update time in the title). That is the reason, I believe, that it is showing the start of the extract time and not the finished.
That being said when using the same function with different connections you may see this as a result:
- Live database connections display the last time the data source was refreshed.
- Live file-based connections display the last time the file was updated.